Vitamin B12 (Cyanocobalamin)
Also known as: cobalamin, cyanocobalamin
Randomized trials and meta-analyses indicate oral cyanocobalamin can correct deficiency in older adults. B12 with other B vitamins lowers homocysteine, but large trials and meta-analyses do not show consistent reductions in cardiovascular events; in people with impaired renal function cyanocobalamin may be harmful. Evidence for short‑term benefit on depressive symptoms is lacking, though longer use in selected at‑risk groups may reduce relapse or onset in some studies.
Last reviewed: 2026-10-14 · 5 indexed studies
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Overview
Vitamin B12 (commonly as cyanocobalamin) is a water‑soluble vitamin used to prevent or treat deficiency and as a nutritional supplement. Randomized and observational human studies have examined its use for depression, homocysteine lowering and cardiovascular outcomes, and as oral therapy for deficiency in older adults.
Mechanism & Function
Mechanism of Action
Cobalamin is an essential cofactor in methionine synthase and methylmalonyl‑CoA mutase, supporting methylation reactions and neuronal/myelin maintenance; supplementation lowers circulating homocysteine when deficient.
Physiological Role
Coenzyme for methylation pathways and odd‑chain fatty acid/amino acid metabolism; required for red blood cell production and nervous system function.
Primary Pathways
Performance / Health Relevance
Maintains normal neurological and haematological function; plausible indirect effects on cognition and mood in people with deficiency via restoration of methylation and correction of anaemia, but direct ergogenic or cardiovascular benefit is not supported by trials.
Evidence Review
Compare Vitamin B12 Forms
Full comparison3 vitamin b12 forms are indexed. Bioavailability, clinical evidence, and best-use cases differ meaningfully between them.
| Form | Evidence |
|---|---|
Vitamin B12 (Cyanocobalamin)This page Oral cyanocobalamin can be effective for treating deficiency in many patients; specific dosing regimens were not reported in the provided abstracts | 57/100 |
| Vitamin B12 (Adenosylcobalamin) Oral bioavailability can be limited by intrinsic factor availability in the stomach. Sublingual forms may bypass some digestive hurdles. Intramuscular injections offer highest bioavailability for severe deficiencies. | 65/100 |
| Vitamin B12 (Methylcobalamin) Oral bioavailability varies significantly (1-5% at higher doses). Gastric intrinsic factor is required for optimal absorption of dietary B12. Methylcobalamin may be better absorbed than cyanocobalamin in some individuals with impaired B12 metabolism. | 65/100 |
Practical Use & Dosage
- Minimum Effective Dose
- Not established in the provided abstracts
- Optimal Range
- Not established in the provided abstracts
- Upper / Caution Level
- Not established in the provided abstracts; caution advised in people with impaired renal function when using high‑dose cyanocobalamin (see safety)
- Timing
- Not established in the provided abstracts
- Best Format
- Oral cyanocobalamin shown to be effective for treating deficiency in elderly patients in randomized studies included in a systematic review
- Bioavailability
- Oral cyanocobalamin can be effective for treating deficiency in many patients; specific dosing regimens were not reported in the provided abstracts
- Absorption Considerations
- Absorption may be impaired in pernicious anaemia or severe malabsorption syndromes; the provided abstracts do not detail dosing adjustments.
Safety & Interactions
Side Effects
- •Generally well tolerated at supplemental doses in trials
- •Potential for adverse effects in people with impaired renal function when given high‑dose cyanocobalamin (reported increase in cardiovascular events in some analyses)
Contraindications
- Known hypersensitivity to cobalamin preparations
Drug Interactions
- •None specified in the provided abstracts
Who Should Avoid
- •People with significantly impaired renal function should use caution with high‑dose cyanocobalamin (evidence of possible harm)
Monitoring
Monitor renal function in people receiving high doses of cyanocobalamin; assess clinical and laboratory markers of B12 status when treating deficiency.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Vitamin B12 (Cyanocobalamin) typically used or indicated?
Vitamin B12 (Cyanocobalamin) is most commonly used for: prevention/treatment of vitamin B12 deficiency, general health / nutritional insurance, adjunctive therapy for depression in at-risk populations, homocysteine lowering in attempts to reduce cardiovascular risk. Coenzyme for methylation pathways and odd‑chain fatty acid/amino acid metabolism; required for red blood cell production and nervous system function.
How does Vitamin B12 (Cyanocobalamin) work?
Cobalamin is an essential cofactor in methionine synthase and methylmalonyl‑CoA mutase, supporting methylation reactions and neuronal/myelin maintenance; supplementation lowers circulating homocysteine when deficient.
What is the recommended dose of Vitamin B12 (Cyanocobalamin)?
The optimal range is Not established in the provided abstracts. with a minimum effective dose of Not established in the provided abstracts. Best taken: Not established in the provided abstracts. Upper / caution level: Not established in the provided abstracts; caution advised in people with impaired renal function when using high‑dose cyanocobalamin (see safety).
What are the side effects of Vitamin B12 (Cyanocobalamin)?
Reported side effects include: Generally well tolerated at supplemental doses in trials; and Potential for adverse effects in people with impaired renal function when given high‑dose cyanocobalamin (reported increase in cardiovascular events in some analyses). Monitoring: Monitor renal function in people receiving high doses of cyanocobalamin; assess clinical and laboratory markers of B12 status when treating deficiency.
Does Vitamin B12 (Cyanocobalamin) interact with medications?
Known or theoretical interactions: None specified in the provided abstracts. Always check with a clinician before combining with prescription medication.
Who should avoid Vitamin B12 (Cyanocobalamin)?
Vitamin B12 (Cyanocobalamin) is generally not recommended for: People with significantly impaired renal function should use caution with high‑dose cyanocobalamin (evidence of possible harm); and Known hypersensitivity to cobalamin preparations.
How strong is the evidence for Vitamin B12 (Cyanocobalamin)?
Evidence level: Moderate (overall score 57/100), based on 5 indexed studies on SuppIndex.
Research & References (5)
Systematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin B12 for depression.
Systematic review and meta-analysis of RCTs of folate and vitamin B12 for depression; included trials of folate and/or B12 with antidepressants or in at‑risk populations.
B vitamins in stroke prevention: time to reconsider.
Meta-analysis discussing B vitamin therapy for stroke prevention, highlighting that cyanocobalamin can accelerate renal decline and increase cardiovascular risk in those with impaired renal function, while benefits appear in participants with normal renal function or when non‑cyanocobalamin forms are used.
B Vitamins as Adjunctive Treatment for Chronic Heart Failure.
Network meta‑analysis / observational report on B vitamins (including synthetic cyanocobalamin) in chronic heart failure patients, assessing effects on vitamin levels and laboratory markers related to cardiovascular severity.
Homocysteine lowering interventions for preventing cardiovascular events.
Cochrane‑style meta-analysis of randomized trials of homocysteine‑lowering interventions (including B12) for preventing cardiovascular events over ≥1 year.
[Update of oral vitamin B12].
Systematic review updating oral vitamin B12 evidence (1990–2007); included randomized studies and prospective cohorts assessing oral cobalamin therapy.
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Vitamin B9 (L-Methylfolate / 5-MTHF)
75/100L-Methylfolate is the principal circulating form of folate and the only form that can cross the blood-brain barrier. It plays a critical role as a coenzyme in one-carbon metabolism, particularly in the methylation cycle. Its direct bioavailability makes it a preferred supplemental form, especially when addressing folate deficiencies or supporting processes requiring efficient methylation, such as neurotransmitter synthesis and homocysteine regulation. Research indicates its efficacy in supporting mood, cardiovascular health, and cognitive function, particularly in populations with impaired folate metabolism.
Research Overview
Moderate EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/vitamin-b12-cyanocobalamin
SuppIndex. (2026). Vitamin B12 (Cyanocobalamin): Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/vitamin-b12-cyanocobalamin
Based on 5 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Often combined with folate and other B vitamins in trials; combinations alter interpretation of effects attributed to B12 alone.