Vitamin B12
Methylcobalamin · Cyanocobalamin · Hydroxocobalamin
An essential vitamin injected for deficiency, energy, and nerve health — well established and very safe.
Class
Essential water-soluble vitamin (cobalamin)
Half-life
Variable; stored in the liver
Evidence
Randomized human trials
Randomized human trials
Supported by randomized controlled trials in humans. Several compounds at this level are FDA-approved for specific indications.
Overview
Vitamin B12 is not a peptide but a genuinely essential nutrient, required for red blood cell formation, DNA synthesis, and nerve function. Injectable B12 is a mainstay of treating deficiency — common in older adults, vegans, people on metformin or acid-reducers, and those with absorption problems — and it is one of the safest injectables available.
Beyond correcting true deficiency, B12 shots are popular for energy and wellness. The honest picture: if you are deficient, replacement can be transformative; if your levels are already normal, extra B12 is simply excreted and the energy boost is largely subjective. Methylcobalamin is the commonly preferred active form.
How it works
- Cofactor for methionine synthase and methylmalonyl-CoA mutase, essential for DNA synthesis and myelin maintenance.
- Required for healthy red blood cell production; deficiency causes megaloblastic anemia.
- Supports nervous-system function; deficiency causes neuropathy.
What the research shows
Researched effects
- Corrects B12-deficiency anemia and neuropathy (well established)
- Improves energy and cognition when deficiency is present
- Minimal added benefit when levels are already sufficient
Limitations & what it won't do
- No meaningful benefit above normal levels beyond correcting deficiency.
- Not a weight-loss or performance aid on its own.
Dosing protocols
These ranges reflect published trials and community protocols. They are reference information, not a prescription. Doses are per injection unless noted.
Replacement / maintenance
1 mg (1000 mcg)Deficiency replacement often starts with more frequent dosing, then spaces out. B12 is very well tolerated.
Reconstitution & measuring your dose
Handling
- Typical vial sizes
- 10 mg
- Suggested BAC water
- 5 mL
- Storage
- Store cool and protected from light; B12 is light-sensitive.
- After reconstitution
- As a solution, generally stable for months refrigerated.
Why 5 mL? B12 is often supplied pre-mixed as a coloured (pink/red) solution. A 10 mg vial in 5 mL gives 2 mg/mL, so 1 mg is ~25 units on a U-100 syringe.
Dose calculator
Draw to
50units
= 0.5 mL · 20 mcg per unit
Concentration
2000 mcg/mL
Doses per vial
10
Side effects
Common
- Injection-site soreness
- Transient flushing
- Very well tolerated
Serious / rare
- Rare allergic reaction to the formulation
- Rare acne flare with high-dose cyanocobalamin
Contraindications & interactions
Use caution if you have
- Kidney disease
Cyanocobalamin is best avoided in favour of methyl/hydroxocobalamin in significant kidney disease.
Medication interactions
- monitorMetformin — Metformin depletes B12 over time — a reason many people on it need supplementation.
What to monitor
- B12 and (if anemic) blood counts
- Symptoms of deficiency
Commonly combined with
References
- Langan RC, Goodbred AJ — Vitamin B12 Deficiency: Recognition and ManagementAm Fam Physician 2017
Research & educational information only — not medical advice.
You must be 18 or older to use this site. The peptides described are presented as research chemicals intended for research purposes only. Most are not approved by the FDA for human use. Dosing ranges reflect what has appeared in the scientific literature or community protocols and are not prescriptions. Nothing here replaces evaluation by a licensed physician who knows your full medical history.
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