Vitamin B12_Dosage, benefits & legal status
Also known as B12, B-12, Methylcobalamin, Methylated B12, Methylcobalamin (B12), Cyanocobalamin, Cobalamin, Mitochondrial B12
The vitamin sold in peptide vials, at prices from $20 to $83 for the same thing.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Vitamin B12?
Plain language first. The technical label stays, but it never stands alone.Overview
An essential vitamin, needed for nerves and red blood cells. Injections are a real, approved treatment when someone is genuinely deficient.
Cobalamin, an essential water-soluble vitamin required for methionine synthase and methylmalonyl-CoA mutase activity. Injectable cyanocobalamin is an approved prescription treatment for B12 deficiency, including deficiency from pernicious anaemia, coeliac disease, bariatric surgery or long-term metformin use.
What it's used for
Sold for energy, mood and metabolic support. Injections correct a genuine deficiency; in people who are not deficient, the evidence for an energy effect is thin.
How does Vitamin B12 work?
What it does in the body, and where.B12 is the most ordinary thing in this catalogue, which is what makes its presence here interesting.
- 01The body cannot make itIt comes from food or supplements, and absorption depends on intrinsic factor in the stomach, which is why gut surgery and pernicious anaemia cause deficiency.
- 02Deficiency is a real diagnosis with a real treatmentInjections bypass the absorption problem, which is why they are an approved prescription treatment.
- 03The energy claim rests on thatCorrecting deficiency restores energy. Giving more to someone who is replete mostly produces expensive urine.
What else is it used for?
Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
- Correcting a diagnosed B12 deficiencyFDA-approved
- Energy and fatigue in people who are not deficientEarly research
- Mood and cognitionEarly research
- Weight loss, as the B12 in lipotropic blendsResearch only
At a glance
Four things to know about Vitamin B12
Evidence
OTC / supplement
Category
Longevity and energy
Common vial
10 mg
Half-life
Stored in the liver for years
How much, and do you cycle it?
The range, and whether you take breaks.Prescription products are dosed by a clinician, varies by product and by why it is being given. No cyclingNo range
A vitamin replaced to correct a deficiency is not cycled.
How long does it stay in the body?
The half-life, and where the figure comes from.Stored in the liver for yearsclinical-guideline
Unlike most of this catalogue, B12 is stored. Liver stores can cover years of intake, which is why deficiency develops slowly.
You can compare this against the whole library to see where it sits.
How do I dose and price it?
Enter your vial and your dose. Pick a mix. We show the draw and the cost.The vial holds a fixed amount of drug. Adding more water does not make more drug, it just spreads it thinner, so you draw a bigger number on the syringe for the same dose.
Choose your mix
Measuring the water1 mL = one full 100-unit syringe.
Your draw
0 / 100 unitsVitamin B12 starts at $19.99 across 16 vendors, typically $5.50 – $7.15 per mg.
20 listings, last read Sep 22, 2026. Shipping and card fees are not included.
How do you store it?
Before mixing, and after.Dry powder in the freezer or fridge. Once mixed, fridge, and use within about a month.
Unmixed lyophilized Vitamin B12 keeps for a long time cold. Once you add water the clock starts: most reconstituted vials hold up for roughly 28 to 30 days at fridge temperature. Keep it out of light, and do not freeze it after mixing.
What are the side effects and cautions?
Known cautions and warnings for this compound.Vendor labels mix units: some give a total in milligrams, some a concentration such as 1 mg/ml or 2,500 mcg/ml. Two vials both described as 10 mg are not necessarily the same amount of B12.
Who should avoid it
- Known cobalt or cobalamin allergy
- Leber's hereditary optic neuropathy, where cyanocobalamin is avoided
- Pregnancy, where a clinician should set any dose
Stop and get help
- Signs of an allergic reaction such as face or throat swelling, hives, or trouble breathing
- Any change in vision
Common effects
- Injection-site soreness
- Usually nothing else
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Vitamin B12 approved?
And where the numbers on this page come from.Not as a medicine. Vitamin B12 is sold without a prescription as a supplement or cosmetic ingredient, which is a different thing from being approved as a drug.
- Injected into muscle and Injected under the skinFDA-approvedApproved as a prescription injectionCyanocobalamin injection is an FDA-approved prescription product for B12 deficiency. A research-labelled vial bought online is not that product, whatever it contains.
- By mouthOTC / supplementSold as a supplementOral B12 is a dietary supplement, sold everywhere without a prescription.
- RouteInto muscle or under the skin, or by mouth
- Checked24 September 2026
- Approved outside the USThis does not change the United States position above.
- DoseFrom product labeling and published use.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Sources
What has happened recently
Oral B12 is a supplement. Injectable cyanocobalamin is an approved prescription product, and a research-labelled vial sold online is not that product.
You can compare this against the whole library, or read how to check a seller.
What else is like Vitamin B12?
Others in Longevity and energy, side by side.If you're weighing Vitamin B12, it's worth reading MOTS-c, Epitalon, and NAD+ in the same class.
The vitamin sold in peptide vials, at prices from $20 to $83 for the same thing.
- Dose
- Prescription products are dosed by a clinician
- How often
- Varies by product and by why it is being given
A shot people use for energy, metabolism, and healthy aging.
- Dose
- 5 up to 10 mg per week (start low, increase slowly)
- How often
- 1-3x per week
A longevity peptide taken in short courses for sleep and anti-aging.
- Dose
- 5 up to 10 mg per day (start low, increase slowly)
- How often
- 10-20 day courses
A cellular fuel taken for energy, focus, and anti-aging.
- Dose
- 50 up to 100 mg per dose (start low, increase slowly)
- How often
- 2-3x/week
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
- Why Does My Peptide Injection Itch or Welt
Injection-site irritation, a histamine reaction, or a true allergy, and how to tell them apart.
- How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
Sources
- Tracked vendor price listings for B12, methylcobalamin and methylated B12(2026)16 vendors list it, priced from $19.99 to $82.99, with sizes given as milligrams, millilitres or micrograms per millilitre.
Last reviewed 24 September 2026