Diets
Vitamin B12 on a vegan diet: what to know
Most nutrition debates have two reasonable sides. B12 on a fully plant-based diet isn't one of them — this one has a clear answer.
Why B12 is different
Vitamin B12 is required to make red blood cells, synthesize DNA, and maintain the myelin sheath around nerves. Deficiency causes megaloblastic anemia and, if prolonged, nerve damage that can become permanent.[1]
The catch is where it comes from. B12 is produced by bacteria, not by plants or animals — animals accumulate it through their own gut bacteria and their food. That means no unfortified plant food is a reliable B12 source. Not spirulina, not nutritional yeast unless it's explicitly fortified, not fermented soy.[1]
How much you need
The adult RDA is 2.4 mcg/day, rising to 2.6 mcg in pregnancy and 2.8 mcg while breastfeeding.[1]
How vegans should cover it
- Fortified foods — many plant milks, breakfast cereals, and nutritional yeast products are fortified. Check the label; fortification is not universal.
- A B12 supplement — the simplest and most reliable route, and widely recommended for anyone eating fully plant-based.
- Don't rely on stores — the liver can hold years' worth of B12, which is exactly why deficiency creeps up slowly and is often missed until symptoms appear.
Vegetarians who eat dairy and eggs are in a much easier position, since both contain B12 — see our vegetarian macros guide.
Keep reading: Vegan macros guide · Plant-based vs. vegan · Plant-based protein sources