Vitamin B12
Cyanocobalamin / methylcobalamin (not a peptide)
Vitamin B12 is an essential vitamin, not a peptide. Cyanocobalamin injection is an approved medicine for treating B12 deficiency.
Regulatory status: Approved. Cyanocobalamin injection has an FDA label for pernicious anaemia and other causes of B12 deficiency.
Default vial
30 mg
Default mix
30 mL
Reported range
100–1000 mcg (label)
Draw (U-100)
100 u
Not a peptide — a vitamin. Cyanocobalamin injection is an approved medicine for B12 deficiency and pernicious anaemia, and usually comes ready-mixed rather than as a powder to reconstitute. Injecting it when you are not deficient has no established benefit.
Where these numbers come from
Cyanocobalamin injection is an approved medicine for B12 deficiency and pernicious anaemia; the dose comes from its prescribing information. It is a vitamin, not a peptide, and no label supports injecting it for energy in people who are not deficient.
Reviewed October 2026
What it is
- A vitamin — cobalamin — not a peptide. It is listed here because it is sold alongside peptides and injected the same way.
- Required for red blood cell formation, DNA synthesis and the nervous system.
- Supplied as a ready-made solution in most cases, so there is usually nothing to reconstitute.
- Given by intramuscular or deep subcutaneous injection when oral absorption is the problem.
How it is described to act
- 1
Injected, which bypasses the intrinsic-factor-dependent absorption that fails in pernicious anaemia.
- 2
Bound to transport proteins in the blood and taken up by tissues; excess is excreted in urine.
- 3
Acts as a cofactor for two enzymes, one in methionine synthesis and one in the mitochondrion.
- 4
In deficiency, replacement corrects the anaemia and can halt neurological progression; in people who are not deficient, there is no established benefit to add.
What the research has looked at
Established medical use
- According to the approved labelling, injectable cyanocobalamin treats B12 deficiency from pernicious anaemia, malabsorption, and related causes.
- Deficiency is a real and common clinical problem, particularly after bariatric surgery, with metformin use, and on diets excluding animal products.
Use without deficiency
- No approved label supports injecting B12 for energy, mood or weight in someone whose B12 is normal.
- B12 status can be measured with a blood test, which makes this one of the few compounds in this library where the question “do I actually need this?” has a straightforward answer.
Strength of evidence: Approved drug (for a specific indication)
An approved medicine with a long clinical record for treating deficiency. That record does not extend to the uses it is marketed for in the peptide world.
This molecule is an approved medicine for at least one indication. Where that is the case, the approved prescribing information — not community convention — governs its use.
Reported cautions and unknowns
- Generally well tolerated in replacement doses; excess is largely excreted.
- The label notes that cobalamin products should be used cautiously in people with suspected Leber's hereditary optic neuropathy.
- Starting B12 in severe deficiency can cause a drop in potassium as red cell production resumes, which is why initial treatment is normally supervised.
- Treating yourself can mask the underlying cause: B12 deficiency is a symptom of something, and correcting the number without finding out why is a missed diagnosis.
References
Handling this vial
- Lyophilized vials are generally stored at 2–8 °C and kept out of light; once reconstituted with bacteriostatic water they are refrigerated and commonly discarded after 28 days.
- Mix by aiming water down the vial wall and rolling gently — do not shake — and never re-freeze a reconstituted vial.
- Pep-Tidy cannot verify what is in your vial. Ask your supplier for a current Certificate of Analysis (HPLC/MS).
Vitamin B12 questions people ask
How do you reconstitute Vitamin B12?
A common starting point for a 30 mg vial of Vitamin B12 is 30 mL of bacteriostatic water, which gives 1 mg per mL. Aim the water down the inside wall of the vial, let it dissolve on its own, and roll gently instead of shaking. Pep-Tidy's reconstitution calculator will recalculate the numbers for any other vial size or water volume you use.
How many units of Vitamin B12 is one dose?
At 1 mg per mL, that works out to about 100 units on a U-100 insulin syringe for a 1000 mcg dose. Change the vial size, water volume, or target dose in the calculator and the syringe reading updates with it. This is arithmetic, not a dosing recommendation.
What dosing schedule is reported for Vitamin B12?
Published and community sources describe 100–1000 mcg (label), intramuscular, once weekly, typically run 12 weeks on. These figures describe what has been reported, not what anyone should take — talk to a licensed clinician first.
How should Vitamin B12 be stored?
Lyophilized Vitamin B12 vials are generally kept at 2–8 °C and out of light. Once reconstituted with bacteriostatic water they are refrigerated and commonly discarded after about 28 days. Never re-freeze a reconstituted vial and never shake it.
Read this before you act on anything above
Everything on this page is a summary of what other people have published — it is not medical advice, not a recommendation, and not a dosing instruction. Reported dose ranges describe what appears in the literature or in community protocols, not what anyone should take. Talk to a licensed clinician before using any peptide.