We use essential cookies (authentication, your saved goals/stack) by default. With your permission we'll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more
Vitamin B12 (Methylcobalamin)
Drives nerve myelination, red blood cell formation, and DNA synthesis — deficiency is common in vegans, vegetarians, and older adults.
What the evidence says
Vitamin B12 appears to help in 14 of 19 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2006–2026 with a typical study size of 770 participants.
Based on 63 studies · 23 meta-analyses · 18 RCTs · 443,898 total participants
Confidence
HighWhat the studies found
By outcome
Vitamin B12 has an evidence score of 9/10 — very strong evidence based on 63 indexed studies, including 21 meta-analyses. Drives nerve myelination, red blood cell formation, and DNA synthesis — deficiency is common in vegans, vegetarians, and older adults.
The commonly studied dose of Vitamin B12 is 500-1000mcg daily for maintenance; higher for deficiency. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Vitamin B12 is in the morning. Taking it with food is preferred. Vitamin B12 (cobalamin) is essential for methylation (methionine synthase), mitochondrial energy production (methylmalonyl-CoA mutase), and myelin synthesis.
B-Complex
Probably helpsEssential B vitamins in their active methylated forms, supporting energy production, mood, and cognitive function.
Methylfolate
Likely helpsBioactive folate that bypasses MTHFR conversion — critical for the 30-40% of people with gene variants affecting mood and methylation.
Last reviewed May 2026 · evidence from 40 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Vitamin B12 is an essential water-soluble vitamin that plays critical roles in neurological function, DNA synthesis, and red blood cell formation. Deficiency is common, especially in vegetarians/vegans, older adults, and those with absorption issues. Methylcobalamin is the active, neurologically-preferred form, while cyanocobalamin is cheaper but requires conversion.
Essential cofactor for methionine synthase
Supports nerve sheath integrity
Required for healthy red blood cell formation
How Vitamin B12 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
500-1000mcg daily for maintenance; higher for deficiency
Loading: For deficiency: 1000-2000mcg daily or injections as directed
Can be taken without food
| Form | Type |
|---|---|
| 💊Methylcobalamin (sublingual) | Recommended |
| 💊Adenosylcobalamin | Alternative |
| 💊Hydroxocobalamin | Alternative |
| 💊Cyanocobalamin (cheapest) | Alternative |
Methylcobalamin is the active form. Sublingual absorption bypasses GI absorption issues.
Minimum: 4 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Sublingual forms bypass absorption issues. Methylcobalamin is preferred for neurological benefits.
You can get vitamin b12 from these foods and drinks. Doses are typical per-serving estimates — actual content varies by brand, brew, cooking, etc.
180 mcg per 3 ozs
3 oz cooked. Preformed retinol (no conversion needed). Don't exceed 1 serving/week if pregnant — vitamin A toxicity risk.
252 mcg per 3 ozs
3 oz cooked. The densest natural source of B12.
Dose-response data unavailable. The current published research for Vitamin B12 does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Improved energy, especially if deficient
Better memory and mental clarity
Prevention/reversal of neurological symptoms
Essential to supplement; B12 only found in animal products
Higher doses often needed due to reduced absorption
Metformin reduces B12 absorption; supplementation often needed
Reduce B12 absorption; consider supplementation
Tip: Take with food
Tip: Reduce dose if persistent
Tip: Discontinue if symptoms occur
Vitamin B12 is generally well-tolerated and considered safe for most healthy adults at recommended doses. The most commonly reported side effects are mild GI upset, acne-like skin eruption (high doses), allergic reaction (rare, usually with injection). Use caution if any of these apply to you: Leber's hereditary optic neuropathy (may worsen); Cobalt or cobalamin hypersensitivity.
Choline
Mixed evidencePrecursor to acetylcholine and phosphatidylcholine — critical for memory, liver function, and cell membrane integrity.
Tap node to isolate • Pinch to zoom • Tap edge for research