Three points on one pathway, and the furthest one works best.
The destination · Cannot enter cells
The coenzyme your cells use in nearly every energy-producing reaction. It is what all three products are ultimately aiming at, and the one form that cannot get into a cell from outside.
One step away · Reinstated 2025
Nicotinamide mononucleotide. One enzymatic step from NAD+ inside the cell. Raises blood NAD+ dose-dependently in human trials, and spent three years unable to be sold as a US supplement.
Two steps away · Never interrupted
Nicotinamide riboside. Two steps from NAD+, and the form your cells have a dedicated transporter for. It has the longest published human pharmacokinetic record of the three.
| NAD+ | NMN | NR | |
|---|---|---|---|
| Steps from NAD+ | It is NAD+ | One | Two |
| Enters cells intact | No [1] | Debated [2] | Yes, via nucleoside transporters [1] |
| Raises blood NAD+ orally | Not established | Yes, dose-dependently [2] | Yes, up to 2.7-fold [3] |
| US supplement status | Sold as a supplement | Excluded 2022, reinstated 2025 [5] | Never interrupted [5] |
| Permitted in Australia | No, still not permitted [6] | Yes, since December 2025, with conditions [6] | Yes, as NR chloride [6] |
| Sold as an IV drip | Widely | Rarely | Rarely |
The three have near-identical biology and completely different legal histories. See the regulatory section.
NAD+ is a coenzyme involved in more than 500 enzymatic reactions, and levels fall with age. NMN and NR are precursors your body converts into it, one step and two steps away respectively. All three are sold on the same promise.
Your cells run on a molecule called NAD+. It shuttles electrons in the reactions that turn food into energy, and it is also the fuel for sirtuins and PARP enzymes. That is where the longevity interest comes from. More than 500 enzymatic reactions depend on it. [4]
Levels fall as you age, and an enzyme called CD38 is a major driver of that decline. Senescent cells accelerate it further. That is the biology the whole category rests on, and it is real. [2]
What to take is the open question. You can buy NAD+ itself, or either of two molecules your body converts into it. They differ by how many steps from the destination they sit, and that turns out to matter more than it sounds.
One term recurs from here on. The salvage pathway is the route your body uses to recycle NAD+ from its own breakdown products instead of building it from scratch. Both NMN and NR feed into that pathway, which is why they work at all.
NR does. NAD+ does not, at all, in the form people buy. As a pyridine nucleotide it cannot undergo direct cellular uptake and is hydrolysed outside the cell to NMN, then cleaved by CD73 to NR, which cells take up through nucleoside transporters.
This is the finding the whole page turns on, and it is counterintuitive enough that most product marketing ignores it.
Start with NAD+ itself, which cannot enter a cell intact. As a pyridine nucleotide it is unable to undergo direct intestinal absorption or cellular uptake when given from outside the body. [1]
What happens instead is that it gets taken apart in the space outside your cells. It is hydrolysed to NMN, then an enzyme called CD73 cleaves that to nicotinamide riboside, and NR is the thing your cells actually take up, through equilibrative nucleoside transporters, before converting it back into NAD+ inside. [1]
Buying NAD+ therefore means buying something that has to be dismantled into NR before any of it is useful.
For NMN the entry route is contested, and the next section sets out why. What is not contested is the outcome: oral NMN raises whole blood NAD+ dose-dependently, so something is reaching circulation regardless of the route. [2]
Only NR has a dedicated transporter. Cells take it up through equilibrative nucleoside transporters and convert it with nicotinamide riboside kinase enzymes. It is the form the pathway is built to accept. [1]
Somebody tested this directly. A randomised, double-blinded, placebo-controlled pilot compared intravenous NR against intravenous NAD+ in healthy adults. Intravenous NAD+ did not significantly raise whole blood NAD+ within 24 hours at all. Intravenous NR did, significantly, against both the NAD+ arm and saline at three hours. [7]
Injecting the precursor beat injecting the destination.
Disputed since 2019. A paper in Nature Metabolism claimed a gene called Slc12a8 encodes a dedicated NMN transporter. Two of its authors hold a patent on that transporter, and it was rebutted in the same journal the same year. The question is still open.
If NMN has a dedicated transporter, it enters cells directly and is genuinely different from NR. If it does not, it converts to NR first and the two are closer than the marketing suggests. The answer matters to anyone choosing between them, and nobody has one.
The claim. In 2019 Grozio and colleagues published in Nature Metabolism under the title "Slc12a8 is a nicotinamide mononucleotide transporter", reporting that the gene is highly expressed in the mouse small intestine and that knocking it down stops NMN uptake. [10]
The disclosure. The paper's own competing interests statement records that two of its authors are named inventors on a patent covering the Slc12a8 NMN transporter, held by Washington University and licensed to a Japanese company. [10]
The rebuttal. Later the same year, the same journal published a paper by Schmidt and Brenner titled "Absence of evidence that Slc12a8 encodes a nicotinamide mononucleotide transporter." [10]
One further detail belongs here. The accompanying News and Views piece celebrating the original finding, under the headline "The elusive NMN transporter is found", was co-written by David Sinclair. [10]
Where it stands. Unresolved. No later work has settled it either way, and both the original authors and the critic have interests: the first hold the patent, and Brenner researches nicotinamide riboside with commercial ties to the company selling it.
So when a product page tells you NMN enters cells directly, it is repeating one side of a dispute that a rebuttal in the same journal has never answered.
Both precursors raise blood NAD+ in randomised human trials. NMN at 300 to 900 mg daily raised it 38 to 45 percent in one trial. NR raised it 2.7-fold from a single 1,000 mg dose. What that accomplishes downstream is much less settled.
Trammell publishes the first human pharmacokinetic trial of nicotinamide riboside in Nature Communications. A single oral 1,000 milligram dose raised NAD+ in blood cells 2.7-fold, with daily dosing sustaining elevations of 2 to 15-fold. Dose-dependent across 100, 300 and 1,000 milligrams in 12 participants. [3]
Martens and colleagues report that 1,000 milligrams daily lowered aortic stiffness in healthy older adults. One of the better downstream signals in the category. [3]
The counterweight. Multiple trials examining mitochondrial outcomes after oral NR find no improvement in mitochondrial respiration or content in human muscle. Raising NAD+ is established, and what it achieves is not. [8]
Yoshino publishes in Science. 250 milligrams daily raised NAD+ metabolites by about 30 percent over 10 weeks and improved muscle insulin sensitivity in prediabetic women. [2]
The FDA excludes NMN from the definition of a dietary supplement, in Category 4 responses to two new dietary ingredient notifications. The reason has nothing to do with safety or efficacy. [5]
Amazon delists every NMN supplement. For most consumers this is how the exclusion is experienced. [5]
A trial in 80 adults finds 300 to 600 milligrams daily for 60 days raised blood NAD+ by 38 to 45 percent and improved six-minute walk distance in middle-aged adults. A separate multicentre dose-response trial at 300, 600 and 900 milligrams confirms dose-dependent increases, with walking endurance improving at the two higher doses. [2]
Australia's TGA issues a safety alert confirming NAD and NMN are not permitted ingredients in listed medicines there. [6]
The Natural Products Association sues the FDA in the District of Columbia District Court, challenging the exclusion. [5]
The FDA reverses itself, in a 26-page letter, confirming NMN is not excluded from the definition of a dietary supplement. Amazon restores NMN listings in October. [5]
All three are sold. One of them cannot get into a cell.
The molecule furthest from the destination is the one that arrives.
NAD+ is what every product in this category is aiming at, and it is the one form that cannot enter a cell. It gets hydrolysed to NMN, then cleaved to NR, and NR is what the transporter accepts. [1]
The inefficiency is not subtle. In a head-to-head pilot, intravenous NAD+ did not significantly raise whole blood NAD+ within 24 hours, while intravenous NR did at three. [7]
Both precursors work, and neither has shown much downstream. NMN raises blood NAD+ by 38 to 45 percent and improved walking distance and insulin sensitivity in specific populations. [2] NR raises it up to 2.7-fold from a single dose and lowered aortic stiffness in one trial. [3] Several trials looking for mitochondrial improvements in human muscle found none. [8]
The honest summary is that raising NAD+ is a solved problem and the reason for raising it is not.
| NAD+ | NMN | NR | |
|---|---|---|---|
| Full name | Nicotinamide adenine dinucleotide | Nicotinamide mononucleotide | Nicotinamide riboside |
| Position | The destination | One step away | Two steps away |
| Cellular uptake | None intact [1] | Contested [2] | Dedicated transporter [1] |
| Best human result | None established | 38 to 45 percent blood NAD+ rise [2] | 2.7-fold rise, single dose [3] |
| Downstream outcome data | None | Insulin sensitivity, walking distance [2] | Aortic stiffness [3] |
| Trials finding nothing | IV form, no rise in 24 hours [7] | Mitochondrial outcomes [8] | |
| US supplement status | Supplement | Excluded 2022, reinstated 2025 [5] | NDI 882, uninterrupted [5] |
| Australia | Not permitted [6] | Permitted since Dec 2025, with conditions [6] | Permitted as NR chloride [6] |
| Branded form | None | MIB-626 as a drug candidate [5] | Niagen [5] |
| Sold as IV | Commonly | Rarely | Rarely |
Because a drug company filed an investigational new drug application for it before anyone filed the supplement paperwork. Under the 1994 DSHEA drug preclusion clause, that excludes an ingredient from the supplement definition. NMN was excluded on 4 November 2022 and reinstated in September 2025, and is lawfully marketable in the United States as of September 2026.
This is the part of the page with no biology in it, and it affected more people than anything else here.
What the FDA actually said. In its own words, the agency "reconsidered and changed its interpretation of one aspect of 21 U.S.C. section 321(ff)(3)(B)" and determined that NMN is not excluded from the dietary supplement definition. It then set aside both of its 2022 letters. [5]
The reasoning was about timing rather than the rule itself: evidence showed NMN had been marketed as a dietary supplement in the United States as early as 2017, which preceded its authorisation for investigation as a new drug.
The sequence, with dates.
| Date | What happened |
|---|---|
| Around 2017 | NMN first marketed as a US dietary supplement |
| 11 October 2022 | FDA Category 4 response to NDI notification 1247, SyncoZymes |
| 4 November 2022 | FDA Category 4 response to NDI notification 1259, excluding NMN from the supplement definition |
| 6 March 2023 | FDA receives citizen petition FDA-2023-P-0872 from the Natural Products Association and the Alliance for Natural Health USA [5] |
| 13 March 2023 | Amazon delists all NMN supplements |
| 7 April 2025 | Australia's TGA issues a safety alert stating NAD and NMN are not permitted ingredients in listed medicines [6] |
| 10 December 2025 | TGA adds NMN to the Permissible Ingredients Determination, with conditions [6] |
| 28 August 2024 | NPA sues the FDA in the District of Columbia District Court |
| 29 September 2025 | FDA responds to the petition, reverses its interpretation, and sets aside both 2022 letters [5] |
| October 2025 | Amazon restores NMN listings |
| 2 December 2025 | FDA reinstates NMN's new dietary ingredient status, with letters to both notifiers [5] |
As of September 2026, NMN is lawfully marketable in the United States as a dietary supplement, subject to standard new dietary ingredient notification rules. [5]
The rule. Under the Dietary Supplement Health and Education Act of 1994, a substance that was first authorised for investigation as a new drug, before being marketed as a supplement, is excluded from the definition of a dietary supplement. The clause exists to stop companies rebranding drug candidates as supplements, and to protect the incentive to develop drugs. [5]
What triggered it. Metro International Biotech filed an investigational new drug application for MIB-626, a crystalline beta form of NMN, and that filing preceded any compliant new dietary ingredient notification from a supplement company. [5]
The company was co-founded by David Sinclair, the Harvard geneticist whose book and public work did more than anyone's to create demand for NMN in the first place. [11]
So the sequence runs in a loop. The researcher who popularised NMN co-founded the company whose drug filing removed it from US shelves.
The company then argued to keep it off. On 20 November 2023 Metro filed a twelve-page letter into the citizen petition docket, stating that it "agrees with FDA that NMN is rightly excluded from marketing as a dietary supplement" and that the agency "should not permit NMN products to be sold as a dietary supplement." [11]
Sinclair's own account is on the record. He has written that the FDA's decision was preceded by a letter from a company "I co-founded but do not manage or control", and that the point of the letter was that Metro had begun clinical trials with a stable crystalline form of NMN made under drug manufacturing standards. [11] Metro's president and chief scientific officer is David Livingston.
One detail complicates the simple version of this story. ChromaDex, the company that sells nicotinamide riboside, filed its own comments into the same docket also agreeing with the FDA that NMN should stay excluded. [11]
The pharmaceutical company developing NMN as a drug and the supplement company selling its main competitor argued for the same outcome. Charles Brenner, the most prominent public critic of Sinclair on this, researches nicotinamide riboside and has commercial ties to the company marketing it.
What happened. On 4 November 2022 the FDA issued Category 4 responses to two notifications, concluding NMN was excluded from the supplement definition. In March 2023 Amazon delisted every NMN product. The Natural Products Association filed a citizen petition, then sued the agency in August 2024. In September 2025 the FDA reversed itself in a 26-page letter, and Amazon restored listings in October. [5]
NR was never touched. It holds a new dietary ingredient notification and self-affirmed GRAS status dating to 2016, and has been sold continuously as Niagen throughout. [5]
Two molecules, two steps apart on the same pathway, and one spent three years unsellable. The difference came down to which company filed which piece of paper first, not to anything about the molecules.
Australia went the other way, and its rules are unusually specific. The TGA issued a safety alert in April 2025 confirming that NAD and NMN were not permitted ingredients in listed medicines. On 10 December 2025 it added NMN to the Permissible Ingredients Determination, making it lawful in listed complementary medicines for the first time. [6]
The conditions are unusually specific, and they are the tightest regulatory framing of any NAD+ precursor anywhere:
| Condition | Requirement [6] |
|---|---|
| Sponsor | Until 10 December 2027, only where SyncoZymes (Shanghai) is primary sponsor, or a secondary sponsor authorised by them |
| Route | Oral only |
| Maximum daily dose | 500 mg |
| Maximum duration | 12 weeks or less |
| Population | Adults only, not pregnant or lactating |
NAD+ itself is still not permitted there at all. As of TGA guidance published in August 2026, NAD, NAD+ and NADH remain outside the list of ingredients allowed in complementary medicines, while NMN and nicotinamide riboside chloride are both on it. [6]
A regulator arrived independently at the same conclusion: the two precursors are permitted and the molecule that cannot enter a cell is not.
Niacin and nicotinamide both raise NAD+ at a few dollars a year against 60 to 150 a month for NMN or NR. Niacin causes flushing through a receptor unrelated to NAD+. Nicotinamide inhibits sirtuins, the enzymes most people are trying to fuel in the first place.
This is the question the category avoids, and it has a real answer.
Two older forms of vitamin B3 also raise NAD+, and both are cheap. Niacin, meaning nicotinic acid, and nicotinamide, also called niacinamide, have been in multivitamins since the 1930s. A bottle of niacin costs a few dollars and lasts months. NMN or NR at research doses runs 60 to 150 dollars a month. [9]
The obvious question is why anyone pays fifty times more.
Niacin's problem is flushing, and at effective doses it is not trivial. At the doses needed to raise NAD+ meaningfully, niacin produces skin redness, warmth and itching that many people cannot tolerate. The mechanism matters here: flushing comes from niacin binding the GPR109A receptor on immune cells in the skin, and has nothing to do with raising NAD+ at all. [9]
It also takes the longer Preiss-Handler route to NAD+, needing more enzymatic steps, and high doses carry liver stress. Niacin does lower LDL and raise HDL, and neither of the other forms does, so it has a genuine role in people who cannot tolerate statins. [9]
Nicotinamide's problem is stranger, and it undercuts the whole premise. It does not cause flushing, because it lacks the structure responsible for it. It raises NAD+ at high doses.
It also inhibits sirtuins. [9] Sirtuins are the NAD+-dependent enzymes behind DNA repair and metabolic regulation, and they are most of the reason anyone wants more NAD+ for longevity purposes. Nicotinamide is a product of NAD+ breakdown and inhibits sirtuins through feedback when it accumulates.
One cheap option makes you flush, then, and the other blocks the enzymes you were trying to feed.
That is the actual argument for the expensive forms. NR does not activate GPR109A, so no flushing, and it does not inhibit sirtuins. [9] The premium is justified by a mechanism, not by marketing. That is an unusual conclusion for this category.
What it does not justify is any particular outcome. Avoiding two known drawbacks is a reason to prefer NR or NMN over the cheap forms. It is not evidence that raising NAD+ achieves anything, and that remains the unsettled question underneath all five options. [8]
NAD+ cannot enter cells and the other two can. NMN raises blood NAD+ by 38 to 45 percent, NR by up to 2.7-fold. NR has never had its legal status interrupted and NMN lost three years.
Shared: all three aim at the same coenzyme · all three are sold for energy and longevity · none is an approved drug for any indication · all three raise a laboratory measurement with unclear downstream meaning
| NAD+ | NMN | NR | |
|---|---|---|---|
| Gets into cells | No | Probably, route contested | Yes, dedicated transporter |
| Raises blood NAD+ | Not shown | Yes | Yes |
| Human PK published | Limited | Yes | Most extensive of the three |
| Outcome data | None | Insulin sensitivity, walking | Aortic stiffness |
| Null findings | IV form at 24 hours | Mitochondrial outcomes | |
| Legal history | Uneventful | Three years excluded | Uneventful |
| Clinic IV market | Large | Small | Small |
Niacin costs a few dollars a year and nicotinamide 20 to 50. NMN and NR run 60 to 150 dollars a month at research doses. NAD+ infusions cost several hundred dollars a session and are the one option shown not to raise blood NAD+ within 24 hours.
| Form | Rough cost | What you get for it |
|---|---|---|
| Niacin | A few dollars a year [9] | Raises NAD+, with flushing |
| Nicotinamide | 20 to 50 dollars a year [9] | Raises NAD+, inhibits sirtuins |
| NMN | 60 to 150 dollars a month [9] | Raises blood NAD+ 38 to 45 percent [2] |
| NR | Similar to NMN [9] | Raises blood NAD+ up to 2.7-fold [3] |
| NAD+ infusion | Several hundred dollars per session | Did not raise blood NAD+ within 24 hours in one pilot [7] |
The price ladder runs opposite to the evidence ladder in one place. NAD+ infusion is the most expensive route in this category and the only one shown not to raise the thing it is sold to raise. [7]
Between the two precursors the cost is similar, so the choice between NMN and NR is not a budget question. It comes down to which evidence you find more convincing, and no trial has compared them.
Prices here are indicative, drawn from commercial sources rather than from our own vendor tracking, and they move. Check current pricing before relying on any figure.
Nobody has shown that raising NAD+ produces a durable clinical outcome. Nobody has compared NMN and NR head to head in a randomised trial. And nobody has explained why intravenous NAD+ remains the most expensive option when it performs worst.
Nobody has compared NMN and NR directly. Both raise blood NAD+ and no randomised trial has put them against each other. Every comparison in circulation sets one trial against another in different people at different doses.
Nobody has shown that raising NAD+ achieves much. That the precursors raise it is settled. Several trials looking for downstream mitochondrial improvements in human muscle found none. [8] The outcome signals that exist, insulin sensitivity and walking distance for NMN, aortic stiffness for NR, come from single trials in specific populations.
Nobody has run a controlled trial of NAD+ infusion for its popular uses. Not for fatigue, not for addiction, not for longevity. The pilot against NR was a tolerability study in healthy adults. [7]
Nobody has established what NMN's contested uptake route means, either. Whether it enters cells intact or converts to NR first is unresolved, and it determines whether NMN offers anything NR does not. [2]
If cost is the constraint, niacin raises NAD+ for a few dollars a year and you tolerate the flushing. If you want the strongest pharmacokinetic evidence, NR has it. If you want the most direct precursor, NMN. If you were considering an NAD+ infusion, the evidence is against it.
Is cost the binding constraint? Niacin raises NAD+ for a few dollars a year, and the trade is flushing at effective doses. [9] That is a real option and the category rarely presents it as one.
Do you want the best-documented option? NR has the longest published human pharmacokinetic record of the three, going back to 2016, and does not carry either drawback of the cheap forms. [3][9]
Do you want the most direct precursor? NMN is one step from NAD+ rather than two, raises blood NAD+ dose-dependently, and has outcome signals in insulin sensitivity and walking distance. [2] Its entry route into cells is still contested.
Were you considering an infusion? The one controlled comparison found intravenous NAD+ did not significantly raise blood NAD+ within 24 hours, while intravenous NR did at three hours. [7] It is also the most expensive route and the least comfortable.
One question sits underneath all four. Raising NAD+ is established for every option here except the infusion. What raising it achieves is not, and choosing between precursors does not resolve that. [8]
No serious adverse events have been reported across published NMN or NR trials at doses up to 1,200 mg daily. Intravenous NAD+ is a different matter, producing moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during infusion.
Consistent across a reasonable number of trials.
A different profile entirely, and the route with the largest commercial market.
Nobody has run these studies. That is different from a clean result.
The oral safety picture for both precursors is reassuring as far as it goes, and it does not go very far. The trials are short, and a category sold for decades of use has months of data.
The intravenous NAD+ picture is worse and it is the route with the largest clinic market. The symptoms are why those infusions run slowly, and the compound producing them is the one that did not raise blood NAD+ within 24 hours. [7]
None of the three appears on the 2026 WADA Prohibited List. The rule that catches this category is the 100 millilitre limit on intravenous infusions per 12 hours outside hospital settings, which a clinic NAD+ drip can breach on volume alone.
None of the three is a prohibited substance.
The rule that catches this category is different. WADA restricts intravenous infusions and injections to no more than 100 millilitres per 12 hour period outside hospital settings, surgical procedures and clinical diagnostic investigations.
A clinic NAD+ infusion can exceed that on volume alone. The substance is permitted and the delivery is the problem.
Oral NMN and NR raise no infusion question at all.
None is an approved drug. NR has been sold continuously as a dietary supplement since 2016. NMN was excluded from the US supplement definition in November 2022 and reinstated on 29 September 2025. Australia permitted NMN from 10 December 2025 and still does not permit NAD+ itself.
None of the three is an approved drug for any indication.
NR has been sold continuously since 2016. It holds a new dietary ingredient notification and self-affirmed GRAS status dating to 2016, sold as Niagen. Its status has never been interrupted. [5]
NMN is lawfully marketable again after a three year gap. Excluded on 4 November 2022 under the drug preclusion clause, reinstated by the FDA in September 2025, and subject to standard new dietary ingredient notification rules since. As of September 2026 that remains the position. [5]
NAD+ itself is sold as a supplement and compounded for intravenous use, and neither route carries an approval for any indication.
Outside the United States the rules differ sharply. Australia's TGA permitted NMN in listed medicines from 10 December 2025, with a single-sponsor restriction running to December 2027, a 500 mg daily cap and a 12 week duration limit. NAD+ itself remains a non-permitted ingredient there. [6] The European Medicines Agency has granted no marketing authorisation, and novel food regulation applies there instead.
MIB-626, the pharmaceutical NMN, is still in development. It completed Phase 1 showing dose-proportional blood NAD+ increases at 1,000 milligrams once daily, and no Phase 3 timeline has been disclosed publicly. [5] That drug candidate is the reason the supplement was excluded in the first place.
What Europe PMC and ClinicalTrials.gov hold for each, on the same rule.
NAD+ has 146 records, NMN 536 and NR 590. 33, 115 and 125 original human studies, 13, 37 and 124 registered trials, respectively.
NAD+: FDA: Category 1 · FDA: Category 1
The published recordNAD+
Papers and trials about NAD+
70 papers tagged human · 33 not reviews or lab · 6 clinical trial publications
13 registered trials · 1 with posted results
Compare this against the whole library →
Category 1RegulatorsCounted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count.
The published recordNMN
Papers and trials about NMN
212 papers tagged human · 115 not reviews or lab · 17 clinical trial publications
37 registered trials · 2 with posted results
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 499 papers and 37 trials indexed in detail.
The published recordNR
Papers and trials about NR
295 papers tagged human · 125 not reviews or lab · 30 clinical trial publications
124 registered trials · 14 with posted results
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 490 papers and 100 trials indexed in detail.
On published evidence, NR. It has the longest human pharmacokinetic record of the three, a single 1,000 mg oral dose raised blood NAD+ 2.7-fold, and it avoids both the flushing that limits niacin and the sirtuin inhibition that comes with nicotinamide.[3][9] NMN is a reasonable alternative with its own dose-dependent trial data.[2] NAD+ itself is the weakest choice, because it cannot enter cells intact.[1]
NR on the evidence that exists, and no trial has compared them directly. A single 1,000 mg oral dose of NR raised blood NAD+ 2.7-fold, and NR is the form cells have a dedicated transporter for.[1][3] NMN raised blood NAD+ by 38 to 45 percent at 300 to 600 mg daily and has outcome signals in insulin sensitivity and walking distance.[2]
No, not intact. NAD+ is unable to undergo direct cellular uptake and is broken down outside the cell to NMN and then to nicotinamide riboside, which is the form cells take up through nucleoside transporters.[1] Anything sold as NAD+ has to be dismantled before any of it is usable.
NMN, on every measure that has been tested. NAD+ cannot enter cells intact and has to be broken down first, while NMN raises blood NAD+ dose-dependently in randomised trials.[1][2] The only direct comparison of the injectable forms found intravenous NAD+ did not significantly raise blood NAD+ within 24 hours.[7]
Yes, since 10 December 2025, and under tighter conditions than anywhere else. The TGA permits it in listed complementary medicines at a maximum of 500 mg daily for no more than 12 weeks, oral route only, adults only, and until December 2027 only where a single named sponsor is involved.[6] NAD+ itself is still not a permitted ingredient in Australia.
Because a drug company filed an investigational new drug application for it before anyone filed supplement paperwork. Under the 1994 DSHEA drug preclusion clause, that excludes an ingredient from the supplement definition.[5] The exclusion was issued in November 2022 and had nothing to do with safety or efficacy.
His company's drug filing triggered it, and he describes his role as more distant than that implies. Metro International Biotech, which he co-founded, filed an investigational new drug application for a pharmaceutical form of NMN, and under the 1994 drug preclusion clause that excludes an ingredient from the supplement definition.[5] Metro then wrote to the FDA in November 2023 agreeing NMN should stay excluded.[11] Sinclair has written that Metro is a company he "co-founded but do not manage or control".[11] ChromaDex, which sells the competing precursor NR, also filed comments supporting the exclusion.[11] The FDA reversed it on 29 September 2025.
Disputed since 2019, and never resolved. A paper in Nature Metabolism claimed a gene called Slc12a8 encodes a dedicated NMN transporter, two of its authors hold a patent on that transporter, and it was rebutted in the same journal the same year.[10] If the claim holds, NMN enters cells directly. If it does not, NMN converts to NR first and the two are closer than the marketing suggests.
Yes in the United States, as of September 2026. The FDA reversed its exclusion in September 2025 and Amazon restored NMN listings the following month.[5] Much of the coverage still online predates that reversal and says NMN is banned. That was true between November 2022 and September 2025. Australia is a separate question and went the other way. NMN was not a permitted ingredient there until 10 December 2025, and is now allowed in listed medicines under strict conditions: 500 mg a day maximum, 12 weeks maximum, oral only, and a single authorised sponsor until December 2027.[6]
No controlled trial has tested it for fatigue, longevity, addiction or any other popular use. What is established is that NAD+ cannot enter cells intact,[1] and that in a head-to-head pilot intravenous NAD+ did not significantly raise blood NAD+ within 24 hours while intravenous NR did at three hours.[7]
Moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during the infusion, all resolving when it finishes.[7] People given intravenous NR in the same review reported only minor tingling and mild cramping.
Unclear, and that is the honest answer for all three. Raising blood NAD+ is well established for both precursors. What it achieves downstream is not. Several trials looking for improvements in mitochondrial respiration or content in human muscle found none.[8] The positive downstream findings, insulin sensitivity and walking distance for NMN and aortic stiffness for NR, come from single trials in specific populations.
You can, and it raises NAD+ for a few dollars a year instead of 60 to 150 a month. The trade is flushing: skin redness, warmth and itching at the doses needed, caused by niacin binding the GPR109A receptor on skin immune cells, a mechanism unrelated to NAD+ itself.[9] Niacin also takes a longer conversion route and carries liver stress at high doses.
Not if longevity is the goal, and it has a specific problem the others do not. Nicotinamide inhibits sirtuins, the NAD+-dependent enzymes behind DNA repair and metabolic regulation, through feedback when it accumulates at high concentrations.[9] Those enzymes are most of the reason people want more NAD+ for longevity, so the cheap flush-free option works against the goal.
NAD+ is the oxidised form and NADH is the reduced form, meaning NADH is carrying the electrons NAD+ has picked up. The two convert back and forth constantly. Products are usually sold as NAD+, and the uptake problem applies either way.
NAD+ cellular uptake and extracellular metabolism. As a pyridine nucleotide, NAD+ is unable to undergo direct intestinal absorption or cellular uptake intact upon exogenous administration. The majority is hydrolysed extracellularly to nicotinamide mononucleotide, which is cleaved by CD73 to nicotinamide riboside. NR is taken up by cells via equilibrative nucleoside transporters and directed toward NAD+ biosynthesis through nicotinamide riboside kinase enzymes. Primary citation: Nikiforov A, et al. J Biol Chem. 2011;286:21767-21778.
NMN human trial evidence. Yoshino J, et al. Science. 2021: 250 mg/day raised NAD+ metabolites approximately 30 percent over 10 weeks and improved muscle insulin sensitivity in prediabetic women. A 2023 trial, n=80, found 300 to 600 mg/day for 60 days raised blood NAD+ by 38 to 45 percent with improved six-minute walk distance in middle-aged adults. A multicentre dose-response randomised trial at 300, 600 and 900 mg/day confirmed dose-dependent blood NAD+ increases, with walking endurance improving in the 600 and 900 mg groups and no serious adverse events. NMN's route of cellular entry is contested, with the question being whether it crosses the membrane intact or is first converted to NR; what is not contested is that oral NMN raises whole blood NAD+.
Trammell SAJ, Schmidt MS, Weidemann BJ, et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nat Commun. 2016. PMC5062546. First human pharmacokinetic trial of NR. A single oral 1,000 mg dose raised peripheral blood mononuclear cell NAD+ 2.7-fold, with daily dosing producing sustained elevations of 2 to 15-fold. Single doses of 100, 300 and 1,000 mg produced dose-dependent increases in the blood NAD+ metabolome in 12 healthy participants. And Martens CR, et al. 2018: 1,000 mg/day NR lowered aortic stiffness in healthy older adults.
NAD+ biology. A coenzyme required for more than 500 enzymatic reactions, central to energy metabolism and the substrate for sirtuins and PARP enzymes. CD38 has been identified as a major driver of age-related NAD+ decline, with senescent cells accelerating that decline by activating CD38-expressing macrophages in ageing tissue.
NMN and NR regulatory history. Primary source: FDA letter hosted on regulations.gov, downloads.regulations.gov/FDA-2022-S-0023-0069/attachment_1.pdf, which states: "On March 6, 2023, FDA received a citizen petition from the Natural Products Association and the Alliance for Natural Health USA asking us to reconsider this position. On September 29, 2025, FDA responded to the petition and explained that the agency has reconsidered and changed its interpretation of one aspect of 21 U.S.C. section 321(ff)(3)(B) and, consequently, we have determined that NMN is not excluded from the dietary supplement definition. Because NMN is not excluded from the dietary supplement definition, we are setting aside our October 11, 2022 and November 4, 2022 letters." The petition response is at regulations.gov/document/FDA-2023-P-0872-2754. The reversal letter was signed by Donald Prater, Principal Deputy Director for Human Foods. FDA reinstated NMN's new dietary ingredient status on 2 December 2025 with letters to both notifiers. The agency's stated basis was evidence that NMN was marketed as a dietary supplement in the US as early as 2017, preceding its authorisation for investigation as a new drug.
Note one unresolved detail. Sources disagree on which NDI notification received which 2022 letter: the FDA letter above refers to responding to NDIN 1259 on 11 October 2022, while a regulatory tracker gives NDIN 1247 from SyncoZymes on 11 October and NDIN 1259 from Inner Mongolia Kingdomway on 4 November. The dates are given here without the pairing.
NMN excluded 4 November 2022 in Category 4 responses to two new dietary ingredient notifications, NDIN 1247 from SyncoZymes and NDIN 1259 from Inner Mongolia Kingdomway, both concluding NMN was excluded from the definition of a dietary supplement under the drug preclusion clause at 21 U.S.C. section 321(ff)(3)(B). The trigger was an investigational new drug application for MIB-626, a crystalline beta form of NMN from Metro International Biotech, a company co-founded by David Sinclair, filed before any compliant NDI notification. Amazon delisted all NMN supplements on 13 March 2023. The Natural Products Association and the Alliance for Natural Health filed citizen petition FDA-2023-P-0872 on 7 March 2023, and NPA sued the FDA in the District of Columbia District Court on 28 August 2024. In September 2025 the FDA reversed its position in a 26-page letter, confirming NMN is not excluded from the supplement definition; Amazon restored listings in October 2025. As of 2026 NMN is lawfully marketable subject to standard NDI notification rules. NR holds NDI 882 and self-affirmed GRAS status dating to 2016, marketed as Niagen, with no interruption. MIB-626 completed Phase 1 showing dose-proportional blood NAD+ increases at 1,000 mg once daily; no Phase 3 timeline has been disclosed.
Australian Therapeutic Goods Administration.
7 April 2025: TGA safety alert addressing products claiming to contain or influence NAD, NAD+, NADH or NMN, reminding sponsors that NAD and NMN were not permitted ingredients in listed medicines at that time.
10 December 2025: NMN added as an ingredient to the Therapeutic Goods (Permissible Ingredients) Determination (No. 4) 2025, making it lawful in Australian AUST L listed complementary medicines for the first time. The TGA subsequently published a compositional guideline specifying the beta-anomer form, assay range, impurity limits and microbiological limits.
Conditions of use, per a TGA safety alert in February 2026: NMN must be used as an active ingredient; until 10 December 2027 it may only be used where SyncoZymes (Shanghai) Co Ltd is the primary sponsor, or where a secondary sponsor has been authorised by that primary sponsor with the TGA notified; oral route only; maximum recommended daily dose 500 mg; recommended duration 12 weeks or less; adults only, not for pregnant or lactating women.
August 2026: TGA guidance on product naming confirms that NAD, NAD+ and NADH are not permitted for use in complementary medicines in Australia, and that using those terms in product names is unacceptable. Nicotinamide, nicotinamide riboside chloride and NMN are permitted.
Randomised, placebo-controlled pilot clinical study evaluating acute intravenous NR and intravenous NAD+ in healthy adults. medRxiv, DOI 10.1101/2024.06.06.24308565. Four arms: NR IV 500 mg, NAD+ IV 500 mg as active comparator, oral NR 500 mg, saline IV as placebo. NAD+ IV did not significantly elevate whole blood NAD+ within 24 hours. NR IV produced a statistically significant increase against both NAD+ IV and saline at 3 hours. This was a preprint at the time of writing; confirm publication status. And Reyna K, et al. Front Aging. Published 2 February 2026. DOI 10.3389/fragi.2026.1652582: retrospective review of records from a commercial wellness clinic chain, four consecutive days of 500 mg NAD+ IV or NR IV. The NAD+ IV group reported moderate to severe gastrointestinal symptoms, increased heart rate and chest pressure during infusions; the NR IV group reported minor tingling and mild cramping. All symptoms resolved on completion. Note that the records came from the commercial clinic selling the infusions.
Dollerup OL, et al. 2018 and 2020, and Remie CME, et al. 2020. Human trials examining mitochondrial outcomes after oral nicotinamide riboside. Found no improvement in mitochondrial respiration or content in human muscle.
Vitamin B3 forms and cost comparison. Niacin (nicotinic acid) raises NAD+ through the Preiss-Handler pathway, which requires more enzymatic steps than the salvage route. Flushing results from niacin binding the GPR109A receptor on immune cells in the skin and is not related to NAD+ elevation. Niacin lowers LDL and raises HDL, unlike nicotinamide or NR, and is prescribed for high cholesterol in patients who cannot take statins. Liver stress is reported at high doses. Nicotinamide (niacinamide, NAM) does not cause flushing, lacking the structure responsible for prostaglandin release, and became the preferred form for nutritional supplementation soon after its identification in the late 1930s. Nicotinamide inhibits sirtuins, accumulating as a product of NAD+ breakdown and inhibiting through feedback; primary citations given in the literature include Bitterman KJ, et al., J Biol Chem. 2002;277:45099-45107, and Guan X, et al., PLoS One. 2014;9:e107729. NR does not activate GPR109A and does not inhibit sirtuin activity. Indicative costs: niacin a few dollars for a bottle lasting months; nicotinamide 20 to 50 dollars a year; NMN or NR 60 to 150 dollars a month at research doses. ** THE NAD+ INFUSION PRICE WAS NOT VERIFIED AND IS STATED ONLY AS AN ORDER OF MAGNITUDE.**
The Slc12a8 dispute. Grozio A, et al. Slc12a8 is a nicotinamide mononucleotide transporter. Nat Metab. 2019;1:47-57. DOI 10.1038/s42255-018-0009-4. The paper's own competing interests statement records that two authors are inventors on patent PCT/US18/46233 covering the Slc12a8 NMN transporter, applicant Washington University, licensed to Teijin Limited. An accompanying News and Views piece in the same issue, "The elusive NMN transporter is found", was written by Lindsay Wu and David Sinclair. Rebuttal: Schmidt MS, Brenner C. Absence of evidence that Slc12a8 encodes a nicotinamide mononucleotide transporter. Nat Metab. 2019;1:660-661. DOI 10.1038/s42255-019-0085-0. The dispute is unresolved. PEER REVIEWED, ABSTRACTS AND COMPETING-INTERESTS STATEMENTS READ.
The Metro International Biotech connection.
Primary document. Metro International Biotech comment letter, 20 November 2023, filed into docket FDA-2023-P-0872 and hosted at downloads.regulations.gov/FDA-2023-P-0872-2745/attachment_1.pdf. Twelve pages. The letter states: "Metro agrees with FDA that NMN is rightly excluded from marketing as a dietary supplement under the drug exclusion clause of the FDCA. FDA should not permit NMN products to be sold as a dietary supplement, which would be in violation of the drug exclusion clause and without sufficient demonstration of safety, adequate directions for use, or compliance with good manufacturing practices." Metro describes itself as a clinical-stage pharmaceutical company developing NMN for Alzheimer's disease, Friedreich ataxia and kidney disease. Its president and chief scientific officer is David Livingston.
The connection. Sinclair co-founded Metro Biotech in 2015 with Washington University professor Rajendra Apte. He is also the author of Lifespan and the most prominent public advocate for NMN, so the compound he popularised was removed from US shelves by a filing from a company he co-founded.
His own words, quoted for fairness: "The FDA's decision was preceded by a letter from MetroBiotech, a company I co-founded but do not manage or control, pointing out that the company had begun clinical trials with a special, crystalline form of NMN that is stable and made under FDA drug standards."
The story is not one-sided. ChromaDex, which markets nicotinamide riboside, filed its own comments into the same docket agreeing with the FDA that NMN is excluded. The pharmaceutical developer and the seller of the competing precursor argued for the same outcome. Charles Brenner, the most prominent public critic of Sinclair on this, researches nicotinamide riboside and has commercial ties to the company marketing it.
**THE LETTER AND ITS QUOTED TEXT ARE **