Glutathione vs NAD+
Both are sold as injections. In both cases, what you inject is not what does the work. NAD+ cannot enter cells intact and has to be dismantled first, and in a head-to-head pilot, injecting its precursor raised blood NAD+ more than injecting NAD+ itself. Glutathione oxidises to an inactive form easily, and oral dosing raised body stores substantially in a six month trial.
- Antioxidant and metabolic
- Neither approved for wellness
- Both have absorption problems
The molecule you inject is not the one that acts.
The FDA has warned compounding pharmacies about injectable glutathione after contamination reports. NAD+ has no approved product anywhere. In both cases the evidence favours a precursor, and a route other than the drip.
| Attribute | Glutathione | NAD+ |
|---|---|---|
| What it is | A tripeptide, 3 amino acids | A nucleotide coenzyme, not a peptide |
| Enters cells intact | Poorly | No, it must be broken down first [1] |
| Best evidence route | Oral, over months [5] | Oral precursors, over weeks [7] |
| FDA position on injection | Warned compounders after adverse events [4] | No approved product |
| An approved precursor exists | Yes. NAC, since 1963 [11] | Nicotinamide riboside, as a supplement [7] |
| Approved for wellness | No | No |
| Clinic availability | Widespread | Thousands of clinics globally [1] |
Both have approved or evidenced uses that are not the ones they are mostly sold for.
Glutathione
Three amino acids joined together, made in every cell in your body. Your main internal antioxidant, and one that falls apart quickly outside a cell.
NAD+
A nucleotide coenzyme your cells use in almost every energy-producing reaction. Levels fall with age, and it cannot get into a cell in the form people inject.
The same problem twice, for two different reasons.
One is a peptide that degrades before it works. One is not a peptide at all and has to be taken apart before it works.
NAD+ cannot enter a cell
As a pyridine nucleotide it cannot be absorbed or taken up by cells intact when given from outside the body. It is hydrolysed to NMN in the space outside your cells, then cleaved by an enzyme called CD73 to nicotinamide riboside. NR is the thing your cells actually take up. [1]
Somebody tested whether skipping that step works better. A randomised, double-blinded, placebo-controlled pilot compared intravenous NR, intravenous NAD+, oral NR and saline in healthy adults. Intravenous NAD+ did not significantly raise whole blood NAD+ within 24 hours. Intravenous NR did, at three hours, and it infused faster and was better tolerated. [2]
So the comparison is not that one worked better. It is that one worked and the other did not register inside a day.
Glutathione falls apart
Glutathione carries a free thiol group on its cysteine residue, and that group oxidises readily. Once it does, the molecule becomes GSSG and stops working. A reconstituted vial left warm or in the light converts on its own. After an infusion, plasma glutathione rises within about thirty minutes and returns toward baseline within a few hours. [6]
The case for injecting it has always been that oral glutathione is poorly absorbed. A six month randomised trial in 54 adults taking 1,000 milligrams a day orally found blood glutathione rose 17 to 30 percent, glutathione in cheek cells rose 260 percent, and natural killer cell activity more than doubled at three months. [5]
That is not what poor absorption looks like.
Only one is a peptide. Glutathione is three amino acids. NAD+ is a nucleotide coenzyme from a different chemical family entirely.
Both have a delivery problem. Different problems, same consequence: what goes in the bag is not what does the work.
Both point away from the drip. NAD+ is better delivered as nicotinamide riboside, and glutathione as N-acetylcysteine, which supplies the rate-limiting building block and has been FDA approved since 1963. [11]
In a head-to-head, injecting the precursor beat injecting the thing itself.
The first infusion clinics
The first clinical description of NAD+ infusion therapy, used for treating multiple addictions. The modern infusion clinic model traces back to here. [1]
The FDA approves N-acetylcysteine
It becomes the standard treatment for paracetamol overdose in the 1980s, working by restoring depleted glutathione stores. Cysteine is the rate-limiting substrate for glutathione synthesis, so supplying it feeds the bottleneck directly. [11]
Real clinical use, for other things
Intravenous glutathione is studied for preventing chemotherapy-induced toxicity and for Parkinson's disease. Across roughly ten trials in those two indications, reported adverse effects were minimal to nil, with no long-term complications. [5]
- real indications
- not the uses being sold
Oral whitening trial
Arjinpathana and Asawanonda run a randomised trial of oral glutathione for skin lightening in 60 Thai medical students, 500 milligrams a day for four weeks. Melanin index fell significantly at two of six measured sites. [5]
Richie six month trial
54 adults at Penn State. Oral glutathione at 1,000 milligrams a day raised blood glutathione 17 to 30 percent, raised glutathione in cheek cells by 260 percent, and more than doubled natural killer cell activity at three months. [5]
- randomised
- six months
- oral route
Trammell pharmacokinetics
The first human pharmacokinetic trial of nicotinamide riboside. A single 1,000 milligram oral dose raised NAD+ in blood cells 2.7-fold, and daily dosing sustained elevations of 2 to 15-fold. Dose-dependent, and measurable within hours. [7]
The counterweight
Multiple trials examining mitochondrial outcomes after oral NR find no improvement in mitochondrial respiration or content in human muscle. Raising NAD+ is well established. What that accomplishes is much less so. [8]
- no functional benefit found
The FDA warning
The FDA warns compounding pharmacies against using dietary-supplement-grade glutathione to make sterile injectables, following adverse events linked to endotoxin contamination. Regulators in the Philippines separately flag unregulated intravenous whitening drips as a public health hazard. [4]
The head-to-head pilot
A randomised, double-blinded, placebo-controlled pilot compares intravenous NR, intravenous NAD+, oral NR and saline in healthy adults. Intravenous NAD+ did not significantly raise whole blood NAD+ within 24 hours. Intravenous NR did, at three hours. The first clinical evaluation of NR given intravenously. [2]
Tolerability in the real world
A retrospective review of records from a commercial clinic chain compares four consecutive days of intravenous NAD+ against intravenous NR. The NAD+ group reported moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during infusions. The NR group reported minor tingling and mild cramping. All symptoms resolved when the infusions ended. [3]
Sold for uses neither was approved for
By a route the evidence does not favour in either case.
Neither compound is a fraud, and that is worth being clear about. Glutathione has genuine trial support in chemotherapy toxicity and Parkinson's disease, where the adverse event record across roughly ten trials was minimal. [5] NR has solid human pharmacokinetics showing it raises NAD+ reliably. [7] The problem is that neither of those bodies of evidence is about the thing being sold, which is an infusion for energy, detox, glow or longevity.
Everything that differs
| Attribute | Glutathione | NAD+ |
|---|---|---|
| Chemical class | Tripeptide, Glu-Cys-Gly | Dinucleotide coenzyme |
| What it does | Neutralises oxidative damage, recycles vitamins C and E, drives phase II detoxification | Accepts and donates electrons in nearly every energy-producing reaction |
| Made in your body | Yes, in every cell | Yes, continuously, by three separate pathways |
| Enters cells intact | Poorly | No [1] |
| Must be converted first | Not to work, but it degrades to an inactive form | Yes, to nicotinamide riboside [1] |
| Best supported route | Oral, in a six month randomised trial [5] | Oral precursors, and intravenous NR over intravenous NAD+ [2][7] |
| Strongest evidence base | Chemotherapy toxicity and Parkinson's disease [5] | Nicotinamide riboside pharmacokinetics [7] |
| Popular use | Skin lightening, detox, wellness | Energy, longevity, addiction recovery, hangover |
| FDA position on injection | Warning to compounders after adverse events [4] | No approved product, widely compounded |
| Approved for the popular use | No | No |
How each one works
Glutathione
Three amino acids, glutamate, cysteine and glycine, made continuously in every cell. The cysteine carries a free thiol group, and that group is where the antioxidant work happens. It neutralises reactive oxygen species, regenerates vitamins C and E after they have been used, and drives the second phase of liver detoxification.
The same thiol that makes it useful makes it unstable. It oxidises to GSSG, the paired inactive form, on contact with air, warmth or light. [6]
NAD+
A coenzyme in nearly every reaction that produces energy in your cells, shuttling electrons back and forth. It is also the substrate for sirtuins and PARP enzymes, and that is where the longevity interest comes from. It does decline with age.
Your body makes it three ways: from tryptophan, from niacin, and by recycling nicotinamide through the salvage pathway. That last route is the one supplements aim at.
These are not obscure compounds with contested mechanisms. Both are central, both are well understood, and both are things your body already makes in large amounts. What is contested is whether putting more in from outside does anything, and by what route.
What separates them
Shared: both are made by your own cells, both fall with age or stress, both are sold as clinic infusions, neither is approved for those uses, and both have real trial evidence for something else.
Glutathione
NAD+
Five gaps, and the first is the one clinics do not raise
Does intravenous glutathione beat oral for anything people buy it for?The IV route has trial support in chemotherapy toxicity and Parkinson's. For skin lightening, detoxification and general wellness, no controlled trial has compared the routes. The one randomised comparison anywhere near this question found oral dosing raising tissue stores substantially. [5]
Does raising NAD+ produce an outcome?That nicotinamide riboside raises NAD+ is well established. [7] Whether that translates into anything measurable is much less clear, and several trials found no improvement in mitochondrial respiration or content in human muscle. [8]
Has anyone run a proper trial of NAD+ infusion for its popular uses?No. The pilot comparison against nicotinamide riboside is the closest thing to controlled data, and it was a tolerability study in healthy adults, not an efficacy trial for fatigue or addiction or anything else. [2]
Has injected glutathione ever been compared against NAC?No. NAC raises glutathione by feeding the rate-limiting step, it is approved, and it is inexpensive. [11] No trial has tested whether an infusion of the finished molecule does anything NAC does not.
What does long-term skin lightening do?One review raises the possibility that systemic administration shifting melanin production could reduce the skin's natural photoprotection. That is a mechanistic concern, not a finding, and it has not been studied.
One has an FDA warning attached. Both have a stability problem.
The glutathione warning
A regulator acting on reported harm, not a theoretical concern.
- The FDA warned compounders against supplement-grade glutathione in sterile injectables [4]fda
- The warning followed adverse events linked to endotoxin contamination [4]harm
- Philippine regulators flagged intravenous whitening drips as a public health hazard [4]advisory
- Skin lightening is an off-label use with no FDA approval anywhereoff-label
Both degrade
Neither compound is stable once it leaves a controlled environment.
- Glutathione's free thiol oxidises to inactive GSSG in warmth or light [6]stability
- Injected glutathione clears from plasma within a few hours [6]clearance
- NAD+ cannot enter cells intact and is broken down extracellularly [1]uptake
- NAD+ infusion produced gastrointestinal symptoms, raised heart rate and chest pressure [3]2026 review
- Compounded material has no verified contents, seized peptides tested 5 to 75 percent pure [10]analysis
The uses being sold
Nobody has run these studies. That is different from a clean result.
- Intravenous glutathione against oral, for any cosmetic or wellness outcomeno trial
- NAD+ infusion for fatigue, longevity or addiction, in a controlled trialno trial
- Whether raising NAD+ produces any functional benefit [8]unresolved
- What repeated systemic skin lightening does to photoprotection over yearsno data
- Injected glutathione against N-acetylcysteine, head to head [11]no trial
*Where this page says nothing is established, it means nobody has studied it. It does not mean a compound is safe.
The glutathione warning deserves context in both directions. Intravenous glutathione given in a hospital setting for chemotherapy toxicity or Parkinson's has a reassuring adverse event record across roughly ten trials. [5] The warning was not about the molecule. It concerned compounders using supplement-grade material to make products intended for injection, and the contamination that followed. [4] What you are buying at a clinic is not what was studied in a hospital. Our guide on reading a certificate of analysis covers what to actually look for.
Neither is prohibited. The drip can still break a rule.
Neither glutathione nor NAD+ appears on the 2026 WADA Prohibited List.
The relevant rule for athletes is different here. A clinic infusion of either compound can breach the volume limit regardless of what is in the bag. The substance is permitted. The volume and the setting are what create the problem.
If you compete under a testing body, check the current infusion rule before booking anything.
Neither is approved for what it is sold for
Glutathione has no FDA approval for skin lightening, detoxification or general wellness. Those uses are off-label at best, and for injectable products there is no approved product to be off-label from.
In 2019 the FDA warned compounding pharmacies against using dietary-supplement-grade glutathione to produce sterile injectable products, after adverse events linked to endotoxin contamination. [4]
NAD+ has no approved product anywhere. It is sold as a dietary supplement in oral form and compounded for intravenous use, and neither route carries an approval for any indication.
Its precursors sit in a different position. Nicotinamide riboside is sold as a dietary supplement with published human pharmacokinetics. [7] That is not an approval either, and it is more than NAD+ itself has.
Both are widely available and neither is illegal to obtain. The gap is not legality. It is that the clinic model has grown up around two compounds whose supporting evidence points at different routes and different indications than the ones being sold.
Questions people ask
Does IV glutathione work better than oral?
No trial has shown that for any cosmetic or wellness use. A six month randomised trial of oral glutathione at 1,000 milligrams daily raised blood glutathione 17 to 30 percent and cheek cell glutathione by 260 percent. The intravenous route has trial support in chemotherapy toxicity and Parkinson's disease, which are not the uses it is mostly sold for.
Can NAD+ get into your cells?
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 your cells take up and convert back to NAD+ inside.
Is NAD+ IV better than oral NAD+ precursors?
No controlled trial supports that, and one comparison points the other way. Three hours after infusion, blood NAD+ was significantly higher in people given intravenous nicotinamide riboside than in those given intravenous NAD+. The NR infusion was also faster and better tolerated.
Why did the FDA warn about glutathione injections?
Because compounding pharmacies were using dietary-supplement-grade glutathione to make sterile injectable products, and adverse events followed that were linked to endotoxin contamination. The warning was about manufacturing practice, not about the molecule.
What is the best way to raise glutathione?
The approved answer is N-acetylcysteine, and it has been since 1963. Cysteine is the rate-limiting building block for glutathione synthesis, so supplying it feeds the bottleneck. NAC is the standard hospital treatment for paracetamol overdose specifically because it restores glutathione stores. Oral glutathione itself also raised body stores substantially in a six month trial.
Is glutathione a peptide?
Yes, a tripeptide made of glutamate, cysteine and glycine. NAD+ is not a peptide at all. It is a nucleotide coenzyme, and it appears in peptide libraries because of how it is sold rather than what it is.
Does NAD+ actually do anything?
Raising NAD+ works, and what that achieves is unresolved. Oral nicotinamide riboside reliably raises NAD+ in human blood cells in a dose-dependent way. Several trials looking for downstream effects found no improvement in mitochondrial respiration or content in human muscle.
Does glutathione lighten skin?
The evidence is weak. A four week randomised trial of oral glutathione in 60 people found a significant reduction in melanin index at two of six measured sites. It is not an approved use anywhere and the FDA has warned about injectable skin-lightening products specifically.
What is the difference between NAD+ and NMN?
NMN is one step closer to your cells than NAD+, and nicotinamide riboside is closer still. Exogenous NAD+ is hydrolysed to NMN, then cleaved by CD73 to NR, and NR is the form cells take up through nucleoside transporters. All three are sold, and the one with published human pharmacokinetics showing reliable NAD+ increases is NR.
What are the side effects of NAD+ IV?
Moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during the infusion, according to a 2026 study reviewing records from a commercial clinic chain. People given intravenous nicotinamide riboside in the same review reported only minor tingling in the tongue, jaw and arm, and mild cramping. All symptoms resolved when the infusion finished.
Does glutathione IV have side effects?
In hospital settings, for chemotherapy toxicity and Parkinson's disease, roughly ten trials reported minimal to nil adverse effects. The documented harm came from a different source: the FDA warned compounders after adverse events linked to endotoxin contamination in products made from supplement-grade material.
Is NAD+ IV worth the money?
No controlled trial has tested NAD+ infusion for fatigue, longevity, addiction or any other popular use. What is established is that NAD+ cannot enter cells intact and that oral nicotinamide riboside reliably raises blood NAD+ in a dose-dependent way.
Are they banned in sport?
Neither substance is prohibited. The infusion volume limit is the issue: WADA restricts intravenous infusions to 100 millilitres per 12 hours outside hospital settings, and a clinic drip can exceed that regardless of contents.
What this page is built on
- 01NAD+ cellular uptake and extracellular metabolism. Primary citation: Nikiforov A, et al. J Biol Chem. 2011;286:21767-21778. As a pyridine nucleotide, NAD+ is unable to undergo direct intestinal absorption or cellular uptake intact upon exogenous administration. It is hydrolysed extracellularly to nicotinamide mononucleotide, cleaved by CD73 to nicotinamide riboside, and NR is taken up by cells through equilibrative nucleoside transporters. NAD+ infusion therapy was first described clinically in 1961 and is now offered in thousands of clinics globally.
- 02Randomised, placebo-controlled pilot clinical study evaluating acute intravenous NR and intravenous NAD+ in healthy adults. medRxiv, DOI 10.1101/2024.06.06.24308565. Human randomised, double-blinded, placebo-controlled pilot. Four arms: NR IV 500 mg, NAD+ IV 500 mg, oral NR 500 mg, saline. NAD+ IV did not significantly raise whole blood NAD+ within 24 hours. NR IV produced a significant increase against both NAD+ IV and saline at 3 hours. Preprint at the time of writing, and the NR studied was a branded product, so commercial interest applies.
- 03Reyna K, Heinzen G, Patel N, Ritter M, Siojo A, Legere H, Pojednic R. Intravenous infusion of NAD+ versus nicotinamide riboside: a retrospective tolerability pilot study in a real-world setting. Front Aging. 2 February 2026. DOI 10.3389/fragi.2026.1652582. Retrospective review of records from a commercial wellness clinic chain. The NAD+ group reported moderate to severe gastrointestinal symptoms, raised heart rate and chest pressure during infusions. The NR group reported minor tingling and mild cramping. All symptoms resolved on completion. Records came from the clinic where the infusions were sold.
- 04US Food and Drug Administration warning to compounding pharmacies regarding dietary-supplement-grade glutathione used to produce sterile injectable products, 2019. Regulatory action following adverse events linked to endotoxin contamination. Regulators in the Philippines have separately flagged unregulated intravenous whitening drips as a public health hazard.
- 05Richie JP, et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr. 2015. NCT01044277. And Arjinpathana N, Asawanonda P. Glutathione as an oral whitening agent. J Dermatolog Treat. 2012. Human randomised controlled trials. Six months, 54 adults: oral glutathione at 1,000 mg a day raised blood glutathione 17 to 30 percent, buccal cell glutathione by 260 percent, and more than doubled natural killer cell cytotoxicity at three months. The 2012 whitening trial, 60 participants at 500 mg a day for four weeks, found a significant melanin index reduction at two of six measured sites.
- 06Glutathione stability and pharmacokinetics. The free thiol on the cysteine residue oxidises to pharmacologically inactive GSSG when a reconstituted vial is left warm or exposed to light. After infusion, plasma glutathione rises sharply within roughly 30 minutes and returns toward baseline within a few hours.
- 07Trammell 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 blood cell NAD+ 2.7-fold, with daily dosing producing sustained elevations of 2 to 15-fold, dose-dependent across 100, 300 and 1,000 mg.
- 08Dollerup 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.
- 09World Anti-Doping Agency. The 2026 Prohibited List, M2 Chemical and Physical Manipulation, intravenous infusion limit. Effective 1 January 2026. Regulatory document.
- 10Janvier S, Cheyns K, Canfyn M, Goscinny S, De Spiegeleer B, Vanhee C, Deconinck E. Impurity profiling of the most frequently encountered falsified polypeptide drugs on the Belgian market. Talanta. 2018;188:795-807. Peer-reviewed analytical study. Purity in seized material ranged from 5 to 75 percent.
- 11N-acetylcysteine regulatory status and mechanism. FDA approved since 1963 and the standard treatment for paracetamol overdose since the 1980s, working by restoring hepatic glutathione. Cysteine is the rate-limiting substrate for glutathione synthesis, and NAC supplies it in a form that crosses cell membranes and the blood-brain barrier. The approved intravenous course opens with a 150 mg per kg loading dose.