What is Vitamin B12?
A water-soluble vitamin essential for nerve function and DNA synthesis.
B12 is found primarily in animal products. Forms include cyanocobalamin (synthetic, stable), methylcobalamin and adenosylcobalamin (active forms). Deficiency causes anemia and nerve damage. Common in vegans, older adults, and those on metformin or PPIs.
What the evidence says
The overall evidence grade for Vitamin B12 is A (strong — consistent, high-quality human evidence (systematic reviews, well-powered RCTs)). Essential nutrient. Deficiency consequences well-documented.
Specific findings with supporting evidence:
- Essential for nerve function. Evidence grade A.
- Deficiency causes irreversible nerve damage. Evidence grade A.
Best-supported outcomes:
- Nerve function.
- DNA synthesis.
- Energy metabolism.
- Red blood cell formation.
Where marketing outpaces evidence:
- The claim that "Methylcobalamin is superior for everyone" is not supported by the evidence (grade B).
- Marketing often overstates: Energy boost in non-deficient people.
- Marketing often overstates: Methylcobalamin always superior.
Dose and timing
The typical effective dose for Vitamin B12 is 2.4–1000 mcg. Higher doses for deficiency or absorption issues.
Take it in the morning. Sublingual may help absorption.
Who it's for, and who should skip it
Most relevant for:
- Vegans and vegetarians.
- Older adults.
- Those on metformin or PPIs.
- People with absorption issues.
Not appropriate for:
- Those getting adequate dietary intake.
Safety and cautions
Caution: Irreversible damage. Prolonged deficiency can cause permanent nerve damage. Testing. Consider testing if at risk of deficiency.
Common mistakes
- Vegans not supplementing.
- Assuming diet provides enough in older age.
- Ignoring symptoms.
- Paying premium for methylcobalamin without need.
Myths vs reality
A common misconception: B12 shots are better than oral. In reality, high-dose oral works for most people with mild deficiency. A common misconception: Methylcobalamin is always superior. In reality, cyanocobalamin is well-absorbed and converts to active forms.
How it interacts with other compounds
- Vitamin B12 works well alongside vitamin b9 — work together; deficiency of one can mask the other.
- Vitamin B12 works well alongside b complex — part of B vitamin family.
Questions people ask
Do vegans need B12? Yes, there are no reliable plant sources. Supplementation is essential.
Methylcobalamin or cyanocobalamin? Both work. Cyanocobalamin is more stable and well-studied.
Editorial note
This guide summarizes the published evidence on Vitamin B12. It is educational content, not medical advice. Confirm with your clinician if you take prescription medications or manage a chronic condition.