Vitamin
Vitamin B12
Vitamin B12 requires 2.4 mcg daily for adult women and 2.4 mcg for men. It works best alongside Methylfolate and Vitamin B12 sublingual.
What Vitamin B12 does
Required for myelin maintenance and red blood cell formation.
Absorption of oral doses above ~2 mcg depends on passive diffusion.
How much you need
| Measure | Adult male | Adult female |
|---|---|---|
| Recommended intake | 2.4 mcg | 2.4 mcg |
| Upper intake level | None established | |
| Typical supplement dose | 1 capsule · 1000 mcg | |
Interactions involving Vitamin B12
4 sourced rules| Pair | Severity | Mechanism | Action |
|---|---|---|---|
| Zinc picolinate × Fortified cerealseparate 2h | Moderate | Phytates in grains and fortified cereals chelate zinc and inhibit its absorption dose-dependently. | Take zinc between meals, or choose a chelated form such as zinc picolinate which resists phytate binding.Source |
| Vitamin B12 sublingual × Metformin | Moderate | Metformin reduces ileal calcium-dependent B12 absorption and alters gut microbiome B12 handling; long-term use lowers B12 status in a substantial minority of patients. | Check B12 at least annually on metformin, and supplement if levels are low-normal.Source |
| Methylfolate × Vitamin B12 sublingual | Synergy | High-dose folate can correct the anaemia of B12 deficiency while nerve damage continues, so B12 status must be adequate whenever folate is supplemented. | Always check B12 before or alongside high-dose folate, especially if you are vegetarian or over 60.Source |
| Vitamin B12 sublingual × Vitamin B6 (P5P) | Synergy | B6, B12 and folate are interdependent in one-carbon metabolism; correcting one without the others can leave homocysteine elevated. | Take the B vitamins together rather than in isolation — a B-complex covers this automatically.Source |