Comparison
Vitamin D3 vs Vitamin B12
Vitamin D3
Hormone-like vitamin synthesized in skin from UVB. Profoundly involved in brain function, mood, and inflammation.
Vitamin B12
Methylcobalamin / cyanocobalamin. Essential for myelin, neurotransmitter synthesis, and methylation. Vegetarians often deficient.
| Field | Vitamin D3 | Vitamin B12 |
|---|---|---|
| Category | vitamin | vitamin |
| Dose range | 0.025–0.125mg | 0.5–5mg |
| Half-life | 360h | — |
| Onset | — | — |
| Evidence | EVIDENCEA | EVIDENCEA |
| Safety | ●●●●● | ●●●●● |
| Legal (US) | USOTC | USOTC |
| PubMed refs | 9200 | 18000 |
The comparison in plain English
Auto-generated from dataVitamin D3 and Vitamin B12 are both in the vitamin category respectively. Vitamin D3 Hormone-like vitamin synthesized in skin from UVB. Vitamin B12 Methylcobalamin / cyanocobalamin.
Bottom line
Vitamin D3 (evidence A, safety 5/5) matches the evidence base of Vitamin B12 (evidence A, safety 5/5). Vitamin D3 has the slightly cleaner safety profile. For users new to either, the higher-evidence option is the safer first try.
Choose Vitamin D3 if
Vitamin D3 is the better fit when your goal aligns with its mechanism (Vitamin D3 (cholecalciferol) is converted to 25-hydroxyvitamin D in the liver and then to the active hormone 1,25-dihydroxyvitamin D (calcitriol) in the kidneys) and the dose range (0.025–0.125mg) suits your protocol. Half-life is 360h.
Choose Vitamin B12 if
Vitamin B12 is the better fit when your goal aligns with its mechanism (Cofactor in two essential enzymatic reactions: methionine synthase (the folate-methionine methylation cycle) and methylmalonyl-CoA mutase (branched-chain amino acid and odd-chain fatty acid metabolism)) and the dose range (0.5–5mg) suits your protocol. Half-life is —h.