Vitamin B12

Strong Evidence
Last reviewed July 2026

Essential for nerve function and red blood cells. Vegans are almost always deficient without supplementation.

Overview

Vitamin B12 (cobalamin) is a water-soluble vitamin essential for red blood cell formation, neurological function and DNA synthesis. It is found almost exclusively in animal products, making vegans and some vegetarians particularly at risk of deficiency. B12 deficiency can develop slowly (liver stores last 3-5 years) and presents as fatigue, anaemia, nerve damage and cognitive problems if left uncorrected. It is one of the most important supplements for anyone following a plant-based diet.

Evidence rating

Strong Evidence

B12 deficiency is well established and its consequences are serious — including potentially irreversible nerve damage. The evidence for supplementation correcting deficiency and preventing its consequences is unambiguous. For those with adequate dietary intake, supplemental B12 does not provide additional energy benefits beyond normal function.

Common uses

  • Strong Evidence
    Preventing and correcting B12 deficiency
  • Strong Evidence
    Supporting normal energy metabolism and reducing fatigue
  • Strong Evidence
    Supporting neurological function and nerve health
  • Strong Evidence
    Red blood cell formation and preventing megaloblastic anaemia

Safety & cautions

Worth checking with a pharmacist if you take medication.

Common forms

MethylcobalaminBest form

The active form. Does not need conversion by the body. Preferred for neurological support.

Cyanocobalamin

Synthetic form. Cheaper and stable. Works well for most people.

Sublingual spray or drops

Absorbed directly into the bloodstream. Useful for those with absorption issues.

Food sources

  • Beef liverApprox. 83mcg per 100g — extremely rich source
  • Sardines (tinned)Approx. 8.9mcg per 100g
  • SalmonApprox. 3.2mcg per 100g
  • EggsApprox. 1.1mcg per 2 eggs
  • Dairy milkApprox. 0.9mcg per 200ml
  • Fortified plant milks and cerealsCheck label — levels vary by brand