Vitamin B12 is found naturally only in animal foods: shellfish, liver, fish, meat, eggs, milk and cheese. Clams and beef liver are the richest sources, and a portion of salmon, tuna or beef provides more than a day’s needs. Plants don’t contain useful amounts, so vegans need fortified foods or a supplement. The NHS says adults need about 1.5 mcg a day (US guidelines set 2.4 mcg). Deficiency is more common in older people, people with pernicious anaemia, and people taking metformin or acid-reducing medicines.
What vitamin B12 does
Vitamin B12 helps the body make red blood cells, keeps the nervous system healthy, and is needed to release energy from food and to use folate. A lack of it causes a type of anaemia and, if it goes on long enough, nerve damage. The NHS notes that some of these problems can be permanent, which is why it’s worth treating early.
How much do you need?
- Adults in the UK: about 1.5 mcg a day, according to the NHS.
- Adults in the US: 2.4 mcg a day, rising to 2.6 mcg in pregnancy and 2.8 mcg when breastfeeding, according to the NIH Office of Dietary Supplements.
The NHS says that if you eat meat, fish or dairy foods, you should be able to get enough B12 from your diet.
Best food sources of vitamin B12
Per portion, calculated from USDA FoodData Central values:
| Food | Portion | Vitamin B12 |
|---|---|---|
| Clams, cooked | 85 g (3 oz) | 84 mcg |
| Beef liver, cooked | 85 g (3 oz) | 60 mcg |
| Sardines, canned in oil | 100 g | 8.9 mcg |
| Salmon, cooked | 100 g | 2.8 mcg |
| Beef burger patty, cooked | 100 g | 2.6 mcg |
| Tuna, canned in water | 100 g | 2.6 mcg |
| Milk, semi-skimmed (2%) | 250 ml glass | 1.4 mcg |
| Greek yogurt, whole milk | 150 g pot | 1.1 mcg |
| Swiss cheese | 30 g | 0.9 mcg |
| Plain low-fat yogurt | 150 g pot | 0.8 mcg |
| Egg, hard-boiled | 1 large | 0.6 mcg |
| Chicken breast, roasted | 100 g | 0.3 mcg |
| Fortified breakfast cereal or plant milk | 1 serving | Varies: check the label |
Liver is very high in vitamin A as well as B12, so the NHS advises avoiding it in pregnancy. Our guide to foods to avoid during pregnancy explains why.
Vitamin B12 for vegans and vegetarians
The NHS notes that B12 isn’t found naturally in fruit, vegetables or grains, so vegans may not get enough. Reliable vegan sources are:
- Fortified foods: some breakfast cereals, plant milks, yogurts, yeast extract and nutritional yeast. Check the label, because not all are fortified.
- A B12 supplement, taken regularly.
Seaweed, spirulina, mushrooms and fermented foods are often described as B12 sources, but they aren’t reliable: they contain little B12, or forms the body can’t use well. Our article on spirulina explains this.
Vegetarians who eat eggs and dairy every day can often get enough, but intake may be low if they eat them only occasionally. Our guide to starting a vegan diet covers B12 and the other nutrients to plan for.
Who is at risk of deficiency?
The NHS lists these main causes and risk groups:
- Pernicious anaemia, an autoimmune condition that stops the stomach absorbing B12 from food. It’s the most common cause of B12 deficiency in the UK.
- Older adults. B12 and folate deficiency affect around 1 in 10 people aged 75 and over, and 1 in 20 aged 65 to 74. Absorbing B12 becomes harder with age.
- Vegans who don’t take a supplement or eat fortified foods.
- People taking certain medicines, including proton pump inhibitors (PPIs) for acid reflux and some anticonvulsants. The NHS also lists B12 deficiency as a possible side effect of metformin, a common diabetes medicine.
- People with gut conditions that affect absorption, such as Crohn’s disease, or who have had parts of the stomach or bowel removed.
Signs of B12 deficiency
The NHS lists:
- Extreme tiredness
- Pins and needles
- A sore and red tongue
- Problems with memory, understanding and judgement
These symptoms develop slowly and overlap with many other conditions. If you notice them, see your doctor for a blood test rather than guessing. Our article on iron-rich foods covers iron deficiency, another common cause of tiredness.
Treatment and supplements
Deficiency is usually treated with B12 injections at first, followed by tablets if the cause is diet, or regular injections if the body can’t absorb it, as with pernicious anaemia. If your body can’t absorb B12 from food, eating more of it won’t fix the problem, which is why diagnosis matters.
For supplements, the NHS says taking 2 mg (2,000 mcg) or less a day is unlikely to cause harm.
One important interaction: the NHS warns that taking more than 1 mg of folic acid a day can hide the signs of B12 deficiency, which can eventually damage the nervous system if it isn’t spotted. This is a particular concern for older people.
Easy ways to get enough B12
- Oily fish twice a week, such as salmon or sardines. Our guide to omega-3 foods lists more.
- Dairy every day: milk in porridge, a pot of yogurt, or a little cheese.
- Eggs for breakfast or lunch.
- Fortified foods if you eat few animal products.
Common questions
Can you get too much vitamin B12 from food?
B12 from food isn’t known to cause harm. The NHS notes there isn’t enough evidence on the effects of high-dose supplements, which is why it suggests staying at 2 mg a day or less.
Do B12 supplements give you energy?
Only if you’re deficient. If your levels are normal, extra B12 won’t make you less tired.
Should older adults take a B12 supplement?
Not automatically. Ask your doctor about a blood test if you have symptoms, take metformin or a PPI, or eat few animal foods.
Is nutritional yeast a good source of B12?
Only if it’s fortified. Nutritional yeast doesn’t naturally contain useful amounts of B12, so check the label for added B12 and the amount per serving.
Do vegan children need B12?
Yes. Children on a vegan diet need a reliable source of B12 from fortified foods or a supplement. Ask your doctor, health visitor or a dietitian for the right amount for their age.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
