Vitamin B12 supplements: who needs one and how much

The short answer

If you eat animal products most days and have no absorption problems, you probably don’t need a B12 supplement: the NHS says you should be able to get enough from meat, fish or dairy, and Germany’s BfR says supplements are unnecessary for healthy people with a balanced diet that includes animal foods. If you are vegan, you do need one, or fortified foods, every week of your life. If you are older or take metformin or acid-reducing medicines, ask your GP for a blood test before buying anything.

Who is most at risk

According to the US National Institutes of Health (NIH), these groups are most likely to run low:

• Vegans, and vegetarians who eat few eggs or dairy products. Breastfed babies of vegan mothers are also at risk.
• Older adults. In US data from 2007–2018, 3.7% of people aged 60 and over were deficient and 12.3% had low-normal levels.
• People taking metformin, which can reduce B12 absorption and blood levels.
• People taking proton pump inhibitors (such as omeprazole) or H2 blockers, which reduce the stomach acid needed to release B12 from food.
• People who have had stomach or weight-loss surgery.
• People with pernicious anaemia, an autoimmune condition and the most common cause of B12 deficiency in the UK. It needs medical treatment, usually injections on the NHS, not a shop-bought supplement.

Why labels say 1,000 µg

The reference intake on UK and EU labels (NRV) is 2.5 µg a day; the NHS puts adult needs at about 1.5 µg, and EFSA’s adequate intake is 4 µg. Yet most B12 products contain 500 or 1,000 µg. The reason is absorption: the body’s main uptake route saturates at very small amounts.

So a 1,000 µg tablet is less extreme than it looks. It is also why small doses spread through the day, such as fortified foods eaten two or three times, work well.

How much to take

For vegans, the UK’s Vegan Society gives three equivalent options:

In the UK, the NHS says up to 2 mg (2,000 µg) a day from supplements is unlikely to cause harm, so all three options sit well inside it. Germany’s BfR takes a much more cautious line for products sold freely: it recommends no more than 25 µg per daily dose. That is a recommendation, not a legal limit, and many products exceed it. If you prefer to stay within it, a 10–25 µg daily tablet covers the Vegan Society’s daily option. For a diagnosed deficiency, your GP will decide the dose, often much higher, or use injections.

Which form to buy

You will see cyanocobalamin, methylcobalamin, adenosylcobalamin and hydroxocobalamin, often with claims that one is “active” or “better absorbed”. The NIH states that there is no evidence that absorption differs by form, and that tablets dissolved under the tongue work no better than swallowed ones. Cyanocobalamin is the most studied and usually the cheapest. Drops, sprays and chewables are fine if they suit you; compare the µg per day.

Getting tested

If you think you might be low, ask your GP for a blood test. The NIH gives these reference points:

• Serum B12: most labs call results below 200–250 pg/ml (about 150–185 pmol/l) low.
• Borderline results (150–399 pg/ml) are worth following up with methylmalonic acid (MMA), the more sensitive marker. MMA above 0.271 µmol/l suggests deficiency, although kidney problems also raise it.

Tiredness, pins and needles or memory problems can have many causes. A test tells you whether B12 is one of them.

What a B12 label may claim

UK and EU law (the Great Britain and EU registers match here) allow vitamin B12 to claim that it contributes to normal energy-yielding metabolism, the normal function of the nervous and immune systems, normal psychological function, normal red blood cell formation, normal homocysteine metabolism, cell division and the reduction of tiredness and fatigue. A product needs only 0.375 µg per daily dose (15% of the NRV) to use these claims. No claim says B12 gives extra energy to people with normal levels.

Examples from our database

Checked for our Spanish and German editions; UK products are next.

• Solgar Vitamin B12 1000 µg (chewable, Spain): 1,000 µg cyanocobalamin a day.
• Yes Vegan! Vitamin B Komplex (Germany): 500 µg B12 plus 400 µg folate a day.
• Multicentrum Mujer 50+ (Spain): 7.5 µg B12 as part of a multivitamin.

See every B12 product we have checked, with doses side by side, on our vitamin B12 page. For other nutrients a vegan diet needs to plan for, see omega-3: fish oil or algae oil and iron and tiredness.