Vitamin B12
Vitamin B12 helps your body make healthy red blood cells and keeps your nervous system working, and it's found naturally almost only in animal foods.
On this page
Why B12 matters
- Red blood cells. Without enough B12 you can develop a type of anaemia.
- Nerves and brain. Long-term deficiency can cause nerve damage that may not fully reverse.
- Energy release from food.
How much you need
Adults need about 1.5 µg a day, and you should be able to get it from a varied diet that includes animal foods1. Food labels use a higher reference value of 2.5 µg, so "100%" on a label covers you comfortably. Taking 2 mg a day or less from supplements is unlikely to cause harm1.
| Who's at risk | Why |
|---|---|
| Vegans | Almost no plant foods contain usable B12, so you need fortified foods or a supplement2 |
| Older adults | Less stomach acid means you absorb less B12 from food |
| People with pernicious anaemia | An autoimmune condition stops B12 being absorbed |
| Long-term metformin or acid-reducing medicine (PPIs) users | Both can lower absorption; ask your GP about testing3 |
Best food sources of B12
| Food | Per 100 g | Per serving | % daily |
|---|---|---|---|
| Mussels, cooked | 24 µg | 24 µg100 g | 1,600% |
| Salmon, farmed, cooked | 2.8 µg | 3.4 µg1 fillet (120 g) | 224% |
| Beef mince, cooked | 2.6 µg | 3.2 µg125 g | 217% |
| Tuna, canned in spring water | 2.5 µg | 2.8 µg1 can (110 g drained) | 183% |
| Cheddar | 1.1 µg | 0.3 µg30 g | 22% |
| Eggs | 0.9 µg | 1.1 µg2 eggs (120 g) | 72% |
| Milk, semi-skimmed | 0.5 µgper 100 ml | 1 µg200 ml glass | 67% |
| Soya drink, B12-fortified | 0.4 µgper 100 ml | 0.8 µg200 ml glass | 51% |
Signs of deficiency, and myths
Symptoms of B12 deficiency anaemia include extreme tiredness, lack of energy, pins and needles, a sore red tongue, mouth ulcers, muscle weakness, disturbed vision and problems with memory or mood6. See your GP if you notice them. Treating it early matters, because nerve damage can become permanent.
MythSpirulina and seaweed are good vegan B12 sources.
FactMost contain B12 look-alikes that your body can't use, so they aren't reliable sources7.
MythYou'd know straight away if you were low.
FactYour liver stores years' worth of B12, so a deficiency can develop slowly and quietly, which is why vegans should use fortified foods or supplements from the start.
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References
- NHS. Vitamins and minerals: B vitamins and folic acid. nhs.uk.
- NHS. The vegan diet. nhs.uk.
- NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. ods.od.nih.gov.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. fdc.nal.usda.gov.
- Public Health England. McCance and Widdowson's The Composition of Foods Integrated Dataset (CoFID). GOV.UK, 2021.
- NHS. Vitamin B12 or folate deficiency anaemia. nhs.uk.
- Watanabe F, Yabuta Y, Bito T, Teng F. Vitamin B12-containing plant food sources for vegetarians. Nutrients. 2014;6(5):1861-1873. doi:10.3390/nu6051861