Vitamin B12: Methyl vs Cyano
Eating mostly plants, taking metformin or simply getting older can all change how much vitamin B12 you get from food. Here you will find the main forms of B12, the tiny daily reference amount, why labels show such high percentages and when to talk to your doctor.
What vitamin B12 is and what it does
Vitamin B12, also called cobalamin, is a water-soluble B vitamin that contains the mineral cobalt. Unlike most water-soluble vitamins, the body can store B12 in the liver for years, so changes in intake can take a long time to show. It is found naturally almost only in foods of animal origin, which is why people who eat few or no animal products often look for fortified foods or supplements.
B12 is involved in making red blood cells and DNA and in keeping nerve cells working normally. To get B12 from food, the stomach needs enough acid and a protein called intrinsic factor, which helps explain why age and certain medicines matter. The roles authorised in the EU are listed word for word in the claims box below.
Forms you'll see on labels
| Form | What to know |
|---|---|
| Cyanocobalamin | The most widely used and most studied supplement form. It is stable and the body converts it into the active forms. |
| Methylcobalamin | One of the two active forms found in the body. Popular in "active" or "methylated" B products. |
| Adenosylcobalamin | The other active form, sometimes combined with methylcobalamin. |
| Hydroxocobalamin | Mostly used in prescription injections given by a healthcare professional. |
| Sublingual tablets and sprays | Dissolve under the tongue or are sprayed in the mouth. Research has not shown any oral form to be clearly superior to the others. |
Examples from our shelves for some of the forms in the table above.
How much vitamin B12: NRV, typical amounts and upper limit
- EU NRV: 2.5 µg a day.
- Common supplement amounts: 2.5–25 µg in multivitamins; 100–1,000 µg in single B12 products.
- Upper limit: EFSA has not set an upper limit, noting no defined adverse effects. UK guidance says that 2 mg (2,000 µg) or less a day from supplements is unlikely to cause harm.
Why are B12 doses so far above the NRV? When you swallow a large dose, the body takes up only a small fraction of it, so products often contain many times the reference amount. A 1,000 µg tablet shows 40,000% NRV, which looks dramatic but reflects this tiny reference value.
Food sources include meat, fish and shellfish, eggs, milk, yoghurt and cheese. For people avoiding animal foods, fortified breakfast cereals, plant milks and nutritional yeast can contribute; check their labels for added B12. Browse options in our vitamin B collection.
Who should check with a doctor or pharmacist first
- People taking metformin, which may lower B12 levels over time.
- People taking stomach acid medicines such as omeprazole, lansoprazole or other proton pump inhibitors and H2 blockers, which can reduce the B12 the body gets from food.
- Anyone who has had stomach or bariatric surgery, or who has a condition affecting the stomach or gut; these people often need a B12 plan set by their doctor.
- Adults over 50, who more often produce less stomach acid.
- Vegans and vegetarians, including during pregnancy and breastfeeding, who should make sure they have a reliable B12 source.
- Anyone taking folic acid at high doses, because high folic acid intakes can hide signs of low B12; a blood test gives a clear answer.
- Children: check the age on the pack and ask a doctor or pharmacist before use.
How to read a vitamin B12 label
- Units: µg and mcg mean the same thing (micrograms). Do not confuse them with mg; 1 mg is 1,000 µg.
- Per serving: check whether the amount is for one tablet, two gummies or several sprays.
- Form: the ingredient list names the cobalamin used, for example "methylcobalamin" or "cyanocobalamin".
- %NRV: very high percentages are normal for B12 and are calculated against the 2.5 µg reference.
- Combinations: B12 often appears with folic acid, iron or other B vitamins. Add up the other nutrients too, especially B6 and folic acid, which do have upper limits.
Bahrain and GCC notes
Many households in the region include vegetarian family members, and plant-based eating is growing, so it is worth checking where B12 comes from in your diet. Sprays and sublingual tablets should be kept below 25°C and out of direct sun. During Ramadan, B12 can be taken at suhoor or iftar, with or without food. See the full range in our vitamin B collection.
Reading a real label
Nature's Bounty Vitamin B12 1000 mcg, 200 Tablets| On the label | What it means |
|---|---|
| 1000 mcg vitamin B12 | mcg and µg are the same unit |
| 40,000% NRV | 1000 µg against the 2.5 µg reference intake |
| No EFSA upper limit | EFSA has not set a tolerable upper intake level for B12 |
| 200 tablets, 1 a day | Over 6 months' supply |
- 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 red blood cell formation
- Vitamin B12 contributes to the normal function of the immune system
- Vitamin B12 contributes to normal psychological function
Applies to products that provide at least 15% of the NRV per daily portion (a 'source of' the nutrient).
Products with Vitamin B12
Always read the label and check the amount per serving.
GlobiFerGlobiFer Forte Plus, 40 TabletsOut of stock
APEXAMAPEXAM Fertisitol, 90 CapsulesBHD27.390
Known NutritionKnown Nutrition Kids Vegan Multivitamin, 2 x 30 GummiesBHD13.860Frequently asked questions
Is methylcobalamin better than cyanocobalamin?
Research has not shown either form to be clearly superior. Cyanocobalamin is the most studied, and the body converts it into the active forms.
Why does my B12 show 40,000% NRV?
The NRV is only 2.5 µg, and the body takes up just a small part of a large oral dose, so products commonly contain hundreds of times the reference amount.
Do vegans need a B12 supplement?
B12 occurs naturally almost only in animal foods, so vegans usually rely on fortified foods or a supplement. A doctor or dietitian can advise on the right approach.
Does metformin affect vitamin B12?
Metformin may lower B12 levels over time. If you take it, ask your doctor whether your B12 should be checked.
