Overview
Cyanocobalamin is the synthetic, crystallized form of vitamin B12 most commonly used in injectable preparations and prescription IM B12 in primary care. It is included in this 'peptide companion' library because B12 — particularly injectable B12 — is widely stacked with peptide regimens (especially GLP-1 / metabolic peptides where appetite suppression risks low B12 intake) and because users routinely ask which B12 form to choose. The companion entry [B12 (Methylcobalamin)](/peptides/b12-methylcobalamin) covers the methylated form preferred in self-injection community practice. The clinical evidence is unambiguous for B12 deficiency itself; the form-preference question (cyano vs methyl) is a real but smaller-stakes editorial conversation rather than a clinical one in most cases.
Mechanism
Cyanocobalamin is converted in vivo to the two metabolically active cobalamin forms — methylcobalamin (cytosolic, methionine synthase cofactor) and adenosylcobalamin (mitochondrial, methylmalonyl-CoA mutase cofactor). The 'cyano' group is replaced during the conversion. The conversion is generally efficient in healthy individuals; rare metabolic errors (cblC, cblG) or severe nitric oxide exposure can impair it.
Evidence by indication
We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.
B12 deficiency (pernicious anemia, dietary deficiency, ileal malabsorption, post-bariatric)
Standard of care for >70 years. Multiple decades of clinical evidence; IM cyanocobalamin reliably reverses biochemical and hematologic markers of B12 deficiency. The pediatric, ileal-resection, and pernicious-anemia populations are clear indications.
Prevention of B12 deficiency in vegan / vegetarian diets
Plant-based diets are essentially B12-free; supplementation (oral or injectable) is non-negotiable for sustained vegan diets. Standard nutritional recommendation.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Adjunct in GLP-1 / GIP-GLP-1 peptide stacks (metabolic peptide users)
Appetite suppression on tirzepatide / semaglutide can reduce B12 intake substantially; metabolic clinics increasingly check B12 status and supplement. The indication is preventive maintenance of normal B12 levels — Tier 1 evidence for that, but 'because of metabolic peptides' is not its own RCT-supported indication.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Energy / fatigue in B12-replete adults
IV-clinic and 'B12 shot' marketing positions B12 injections as a general energy boost. There is no RCT showing benefit of B12 in adults with normal B12 levels. The energy effect is a placebo / clinic-context phenomenon for most users.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Studied dose ranges
The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.
Standard primary-care protocol for B12 deficiency: 1000 mcg IM daily x 1 week, then weekly x 4 weeks, then monthly maintenance. Some clinics use 1000 mcg every 1–3 months long-term for pernicious anemia.
Self-injection community use is typically 1000–5000 mcg SubQ 1–2× weekly. SubQ is preferred to IM for self-administration (smaller needle, less painful). Higher doses are reported but are pharmacokinetically wasteful — once tissues are saturated, additional B12 is excreted in urine.
Contraindications
- Leber's hereditary optic neuropathy (LHON) — cyanocobalamin is contraindicated; can accelerate vision loss. Methylcobalamin or hydroxocobalamin is preferred. This is the single hard form-specific contraindication.
- Cobalt or cobalamin hypersensitivity
- Active treatment for cyanide poisoning (cyanocobalamin contains a cyanide group; acute cyanide exposure should use hydroxocobalamin instead)
- Pregnancy (oral or IM B12 is generally safe in pregnancy at standard doses; cyanocobalamin is the most-studied form)
Reported side effects
- Injection-site pain, redness, mild swelling (IM more than SubQ)
- Headache
- Skin rash, pruritus (rare)
- Diarrhea, mild GI upset
- Hypokalemia during rapid correction of severe megaloblastic anemia (clinical-trial-relevant; check potassium during treatment)
- Anaphylaxis (extremely rare; usually attributed to preservatives in injectable formulations)
Reconstitution & storage
Most prescription cyanocobalamin (1000 mcg/mL) ships as a pre-mixed liquid, no reconstitution needed. Compounded high-concentration formulations may be lyophilized; reconstitute per pharmacy instructions. SubQ injection volumes are typically 0.5–1 mL.
Storage. Pre-mixed liquid: refrigerate per label. Some formulations are stable at room temperature. Protect from light — B12 is photosensitive.
Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.
Editorial note
DRAFT — pending Wayne's review. Pairs with the existing methylcobalamin entry. Editorial position: name the LHON-specific contraindication clearly (this is the one place where the form choice is medically meaningful), and refuse to dignify the 'energy shot for B12-replete adults' marketing with anything above Tier 4. The metabolic-peptide-stacking framing is a real, currently-trending use case worth surfacing.
Citations
- [1]Vitamin B12 (cobalamin) deficiency in elderly patientsAndrès E, Loukili NH, Noel E, et al. · Canadian Medical Association Journal · 2004 · PMID 15289284Comprehensive clinical review of B12 deficiency in older adults — anchor for the Tier 1 deficiency indication.View source