Vitamin B12 (cobalamin) occurs naturally only in animal foods, plus in fortified foods and supplements. Most people who eat meat, fish, eggs or dairy get enough from food, so a supplement mainly matters for people who eat no animal products, older people and people on certain medicines, who should talk to a doctor. Only a blood test can tell whether you are short of B12.
If you do decide on a supplement, three things decide the choice: the dose in µg, the form (cyanocobalamin, methylcobalamin) and the format (tablet, lozenge). This guide covers each.
What vitamin B12 is and where it comes from
B12 is a water-soluble vitamin that contains cobalt, which is why its forms are called cobalamins. NIH lists clams, beef liver, fish, meat, eggs and dairy as natural sources. Plant foods contain no reliable B12, so vegans rely on fortified foods such as some plant drinks, cereals and nutritional yeast, or on supplements. The body stores B12 in the liver, so a shortage tends to develop slowly.
Who may not get enough B12
- Vegans and some vegetarians, because B12 is found in animal foods.
- Older adults. Food-bound B12 needs stomach acid to be released, and acid production often falls with age. Supplement B12 is not bound to food, so it does not need that step; NIH therefore suggests that people over 50 get B12 mainly from fortified foods or supplements.
- People who take metformin, or acid-reducing medicines (proton pump inhibitors, H2 blockers). NIH notes that these medicines can lower B12 absorption.
- People with digestive conditions or stomach or bowel surgery.
If you belong to one of these groups, talk to your doctor about a test instead of starting a supplement on a guess. Everyday complaints such as tiredness have many possible causes, so we do not list symptoms. Folic acid can hide the blood changes that a B12 shortage causes while nerve problems go unnoticed (NIH), which is another reason to test first.
Pregnant and breastfeeding women who eat no animal products should talk to a doctor or midwife about B12, because it also affects what the baby receives. EFSA sets the adequate intake at 4.5 µg a day in pregnancy and 5 µg during lactation. On fortified foods such as plant drinks and cereals, look for the "vitamin B12" line in the nutrition table and compare the amount per portion, because manufacturers fortify differently. A supplement and fortified foods do not exclude each other, so both can fit.
The B12 test
A doctor can check B12 in a blood sample and, if the result is unclear, add other markers such as homocysteine. Reference ranges differ between labs, so read the result against the range printed on your own sheet. If you already take B12, tell the doctor, because a supplement taken before the test can change the number.
B12 forms compared
The label should name the form. All of them count as vitamin B12 in the EU health claims.
| Form | What it is | Good to know | In our range |
|---|---|---|---|
| Cyanocobalamin | synthetic form, very stable | the body converts it to the active forms; the most common form in supplements | 1000 µg and 500 µg tablets with folic acid |
| Methylcobalamin | one of two active forms | works directly as a coenzyme | 100 µg and 1000 µg |
| Adenosylcobalamin (5-deoxyadenosylcobalamin) | the other active form | rarely sold on its own | not stocked |
| Hydroxocobalamin | natural form | the body converts it | not stocked |
NIH describes methylcobalamin and adenosylcobalamin as the active forms and cyanocobalamin and hydroxocobalamin as forms the body converts. We know of no reliable head-to-head data showing that one form works better in healthy people, so choose by dose, format and price per day. See the vitamin B12 and B-complex collection.
NOW Foods
Vitamin B12, 1000 µg, 100 Lozengesµg and % NRV: how to read the dose
The EU reference intake (NRV) for B12 is 2.5 µg. EFSA sets an adequate intake of 4 µg a day for adults, and NIH gives 2.4 µg as the recommended amount. Supplements contain far more than that, so labels show very large percentages:
| B12 per daily dose | % of NRV (2.5 µg) | Example in our range |
|---|---|---|
| 100 µg | 4000% | OstroVit methylcobalamin tablet |
| 500 µg | 20000% | Swanson, half a tablet |
| 1000 µg | 40000% | NOW Foods lozenges |
The reason is absorption. Only a small share of a large oral dose is absorbed; NIH puts it at about 10 µg out of a 500 µg supplement in healthy people. Neither EFSA nor NIH has set an upper limit for B12, because intakes well above the need have not shown harm in healthy people. That is not a reason for more: a higher number does not give a higher effect. Doses of several hundred µg a day are common on labels, but if you are pregnant or breastfeeding, take medication or plan a long course, ask your doctor first.
Tablet, lozenge or sublingual
B12 in a supplement does not need stomach acid to be released, so a swallowed tablet works for most people. Lozenges and sublingual tablets are held in the mouth. We know of no convincing evidence that sublingual B12 is better in healthy people, so pick the format you will take every day. Read the ingredients: lozenges use sweeteners such as sorbitol or fructose, and labels warn that excessive consumption may produce laxative effects. Check the label of your product for fish, folic acid or other additives.
How to choose a B12 supplement
- Decide with your doctor if you belong to a group at risk of low B12.
- Find "vitamin B12" on the label and its dose in µg. Ignore the % NRV for comparison, it only scales with the dose.
- Choose a form. Cyanocobalamin and methylcobalamin are both on the label as vitamin B12.
- Choose a format: swallowed tablet, lozenge or sublingual tablet.
- Check what else is in it. Some B12 products add folic acid, which has its own line on the label (NRV 200 µg).
- Work out the price per day, not per pack. A half-tablet dose doubles the days a pack lasts.
If you also take a B-complex or a multivitamin, add up the B12 from all of them. Our multivitamins show the B12 per daily dose on each product page.
What EU law lets us say about vitamin B12
Regulation (EU) No 432/2012 lists the authorised claims. They apply to products that provide at least 15% of the NRV (0.375 µg of B12) per daily dose, whatever the form:
- Vitamin B12 contributes to normal red blood cell formation.
- Vitamin B12 contributes to the reduction of tiredness and fatigue.
- Vitamin B12 contributes to normal energy-yielding metabolism.
- Vitamin B12 contributes to normal functioning of the nervous system.
- Vitamin B12 contributes to normal psychological function.
- Vitamin B12 contributes to the normal function of the immune system.
- Vitamin B12 contributes to normal homocysteine metabolism.
- Vitamin B12 has a role in the process of cell division.
These statements describe B12 as a nutrient. They say nothing about treating a deficiency, and a supplement is not a substitute for a varied diet.
FAQ
What is vitamin B12 for?
The EU register allows these statements for B12: Vitamin B12 contributes to normal energy-yielding metabolism. Vitamin B12 contributes to normal functioning of the nervous system. Vitamin B12 contributes to normal red blood cell formation.
Which foods contain B12?
Meat, fish and shellfish, liver, eggs and dairy. Plant foods have no reliable B12, so vegans use fortified foods or supplements.
Can I take too much B12?
No upper limit has been set by EFSA or NIH, and the extra is mostly not absorbed. Still, keep to the dose on the label, and talk to a doctor about high doses if you are pregnant, take medication or are unwell.
Is methylcobalamin better than cyanocobalamin?
We know of no reliable evidence that it is better in healthy people. The EU claims are the same, so choose by dose, format and price per day.
Do vegans need a B12 supplement?
Plant foods do not supply B12 reliably, so fortified foods or a supplement are the usual route. Ask your doctor about a test and a dose.
I take metformin or an acid-reducing medicine. Should I take B12?
These medicines can lower B12 absorption. Ask your doctor or pharmacist; they can check your level and advise you.
Sources
- Regulation (EU) No 432/2012, authorised health claims
- Regulation (EU) No 1169/2011, Annex XIII (reference intakes)
- EFSA: Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12) (2015)
- NIH Office of Dietary Supplements: Vitamin B12 fact sheet for health professionals
Content reviewed by Inese Kalniņa, dietitian.
