Vitamin B12

The supplement every vegan needs.

• Supplement: everyone
• Last checked: Oct 2026

If you read only one page on this site, make it this one. B12 is easy to get right, and the cost of getting it wrong can be serious and permanent.

Why you need it

Vitamin B12 keeps your nerves healthy and is needed to make red blood cells and DNA. Your body can’t make it, so it has to come from what you eat or take.

Why it matters for vegans

B12 is made by bacteria — not by plants, and not by animals. Plant foods don’t contain reliable amounts of it, so a vegan diet without a deliberate source of B12 will eventually run short. The Academy of Nutrition and Dietetics puts it plainly: vegans need reliable sources of B12, such as fortified foods or supplements.

Two things make it sneaky:

• It runs out slowly. The body keeps a store that can last a long time, so feeling fine after months without B12 proves nothing.
• The warning signs can be hidden. A shortage can cause anaemia, tiredness and nerve damage — numbness, tingling, problems with balance or memory. Plenty of folate, which a vegan diet usually has, can hide the anaemia while the nerve damage carries on. That damage is not always reversible.

Where to get it

Reliable:

• Fortified foods — many plant milks, yogurts, breakfast cereals and nutritional yeasts have B12 added. Check the label: not all of them do.
• Supplements — cheap, small, and the simplest way to be sure.

Not reliable: spirulina, dried nori and most other seaweeds, barley grass, and the bacteria in your own gut. Studies of vegans have shown all of these to be inadequate sources.

Should you supplement?

Yes — unless you reliably eat enough fortified food every day. The Vegan Society recommends one of these:

1. Fortified foods two or three times a day, adding up to at least 3 µg a day, or
2. One supplement a day with at least 10 µg, or
3. One supplement a week with at least 2000 µg.

These numbers are much higher than the official daily reference values — the European Food Safety Authority sets an adequate intake of 4 µg a day for adults — because your body can absorb only a small amount of B12 at once. The bigger and rarer the dose, the smaller the share you absorb, so the dose goes up to make up for it.

No upper limit has been set for B12, because it has a low potential for harm, even at high intakes.

If you are pregnant or breastfeeding, your needs are higher and your baby depends on your B12. If you are raising a vegan child, they need a reliable source too. In both cases, talk to a doctor or dietitian.

How to check your levels

If you have been vegan for a while, or you’re not sure your intake has been reliable, ask your doctor for a blood test — and tell them you’re vegan.

• Serum B12 is the usual test, but on its own it can look normal even when you are short.
• Methylmalonic acid (MMA) is the most specific marker of B12 status. A normal MMA level means your body has enough.
• Homocysteine rises when B12 (or folate) is low. The Vegan Society suggests aiming for below 10 µmol/L.

If a test shows you are low, don’t just start a supplement on your own — let your doctor guide how to bring your levels back up.

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