Vitamin B12: what you need to know
Vitamin B12 is the only nutrient vegans cannot reliably get from plant foods. Fortunately this is easy to solve with a supplement or with fortified foods. Vegetarians who eat little dairy or few eggs can also run short of B12.
In short: choose one of these three
every dayfortified foods spread over at least two meals, together at least 3 µg
every daya supplement with at least 10 µg
every weekone supplement with 2,000 µg
These are the options of The Vegan Society. Official daily intakes differ per country: 1.5 µg in the UK (NHS), 2.4 µg in the United States and 4 µg in the European Union (EFSA). The body absorbs only a small amount of B12 at a time. That is why the dose has to be higher when you take it less often.
No safe upper limit has been set for B12. No harmful effects of a high intake are known.
What does vitamin B12 do?
Vitamin B12, also called cobalamin, is a water-soluble vitamin. You need it to make red blood cells. It is also needed for a healthy nervous system and to make DNA. B12 also plays a role in the metabolism of fats and proteins.
Where does B12 come from?
No plant or animal makes B12 itself. Only certain bacteria do. Animals get B12 from bacteria in their gut or through their feed. In livestock farming many animals receive B12 or cobalt as a feed additive. That is how it ends up in meat, milk and eggs.
Bacteria in our own large intestine also make B12. But they sit too low in the gut: the body can no longer absorb that B12 there.
No reliable plant source
Seaweed, spirulina, tempeh, miso and other fermented foods are sometimes named as B12 sources. Reliable research shows that they mainly contain inactive forms. These sometimes count in a test, but the body cannot use them. They can even hide a deficiency. Plant foods only provide B12 when it has been added. This is the case for many plant milks, breakfast cereals and yeast flakes. Check the label.
How does the body absorb B12?
Absorption needs a protein from the stomach: the intrinsic factor. With it the small intestine absorbs only a few micrograms per meal. On top of that about 1 percent of a high dose passes through the gut wall by itself. That is why one high dose a week also works.
Older people often make less stomach acid. As a result they absorb B12 from ordinary food less well. Some medicines also reduce absorption, such as stomach acid blockers and metformin (for diabetes).
What happens with a deficiency?
The body keeps a store of B12 in the liver. It can last for years. That is why a deficiency often shows up late. Symptoms include:
- tiredness, paleness and shortness of breath due to anaemia;
- pins and needles or numbness in hands and feet;
- memory and concentration problems;
- problems with balance and coordination.
Nerve damage can be permanent. So do not wait for symptoms but take B12 from the start. Note: a lot of folic acid can hide the anaemia while the nerve damage continues.
Take extra care
- Pregnancy and breastfeeding: the need is higher. In the EU the advice is 4.5 µg a day during pregnancy and 5 µg while breastfeeding. A baby gets its B12 from the mother. A deficiency in babies can quickly have serious consequences.
- Children who eat vegan also need B12. Discuss the dose with your doctor or health visitor.
- Older people and people who use stomach acid blockers or metformin absorb B12 less well.
- In doubt? Ask your doctor for a blood test. Often the B12 level in the blood is measured first. More informative are "active B12" (holoTC), methylmalonic acid (MMA) and homocysteine.
Choosing a supplement
B12 tablets are sold in pharmacies, supermarkets and health food shops. Many are vegan, without gelatine. Cyanocobalamin is the best studied form and keeps well. Methylcobalamin is also widely sold. A chewable or sublingual tablet is fine. Choose a supplement with only B12 or a multivitamin that contains enough B12.
Do you get enough nutrients every day? Take the test.
Sources: NHS, B vitamins and folic acid; The Vegan Society, What every vegan should know about vitamin B12. This page is based on an article by Lyra Alves in the magazine of EVA (2004) and was updated in October 2026. This is general information, not medical advice.
See also: Do vegetarians have a greater risk of iron deficiency than meat eaters?. |
