Nutrientspmol/l · nmol/l

B12 (holo-TC) + folate

Optimal

B12 > 300 pmol/l (holo-TC > 50); folate > 15 nmol/l; homocysteine < 10 is the real yardstick

Why

The two methylation vitamins; deficiency causes anaemia, nerve damage and high homocysteine. B12 deficiency hits 20% over 60, 50–80% of vegans, 30% of metformin and PPI users — and plain serum B12 misses half the cases. In VITACOG, supplementation halved brain shrinkage in people with high homocysteine.

How often

Yearly over 60, in vegans, on metformin/PPI; otherwise every 3–5 years.

What moves it

B12 1,000 µg (methyl- or cyanocobalamin) orally — enough even with malabsorption; folate from food (leafy greens, legumes) or 400 µg methylfolate; less alcohol.

Sources

Smith AD et al. Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment – VITACOG. PLoS ONE (2010) ↗

Last reviewed: 6 September 2026

This site is educational and does not replace medical advice. Start any supplement or drug only after consulting a doctor or pharmacist.