Vitamin B12 helps the body make red blood cells and DNA and keeps nerve cells working. It is found naturally in animal foods such as meat, fish, eggs and dairy, and it is added to some fortified foods like breakfast cereals and plant milks. Most people who eat animal products get enough from their diet, but some groups absorb less or eat little or none.
When you compare B12 supplements, you are mainly choosing between different forms of the vitamin, different strengths and different formats, such as swallowable tablets, lozenges or liquids. The doses on labels are often far higher than the daily recommended amount, which can look confusing at first. This guide explains why.
This is general information, not medical advice. If you think you might be low in B12, or you have symptoms such as unusual tiredness, tingling in your hands or feet, or balance problems, see a doctor. A blood test can show whether you are deficient, and some causes of deficiency need treatment that a supplement from a shelf cannot replace.
Who is more likely to need B12
The US National Institutes of Health Office of Dietary Supplements (NIH ODS) lists several groups who are more likely to have low B12 levels:
- Older adults: many have less stomach acid, which the body needs to release B12 from food.
- People with pernicious anaemia: an autoimmune condition that prevents B12 absorption from the gut. It is usually treated by a doctor, often with injections.
- People with digestive conditions or surgery: such as coeliac disease, Crohn’s disease or weight-loss surgery.
- Vegans and some vegetarians: because B12 occurs naturally almost only in animal foods.
- People taking certain medicines: NIH ODS mentions metformin for diabetes and acid-reducing medicines such as proton pump inhibitors and H2 blockers.
If you belong to one of these groups, ask your doctor or pharmacist whether a supplement or a test makes sense for you.
The forms on the label
You will see several chemical names on B12 products. All of them are forms of vitamin B12, also called cobalamin.
| Form | Notes |
|---|---|
| Cyanocobalamin | The most common form in supplements and fortified foods; stable and usually the cheapest |
| Methylcobalamin | A form that occurs naturally in the body; common in lozenges and sublinguals |
| Adenosylcobalamin | Another natural form; sometimes combined with methylcobalamin |
| Hydroxocobalamin | Often used in injections prescribed by doctors |
NIH ODS states that research has not shown any one form of B12 to be better than the others for most people. That means a cyanocobalamin tablet such as Superior Source B12 Cyanocobalamin and a methylcobalamin lozenge such as BioClinic Naturals B12 Methylcobalamin can both be reasonable choices. Price, format and personal preference can guide the decision. The full selection is in the vitamin B category.
Understanding the dose
The recommended dietary allowance (RDA) from NIH ODS is 2.4 mcg a day for adults, 2.6 mcg during pregnancy and 2.8 mcg while breastfeeding. Yet many supplements contain 500 mcg, 1,000 mcg or even 5,000 mcg. The reason is absorption: the body absorbs only a small share of a large oral dose. NIH ODS gives the example that healthy people absorb only about 10 mcg from a 500 mcg supplement.
NIH ODS has not set an upper limit for B12, because it has a low potential for harm at the doses found in food and supplements. Even so, it makes sense to pick the dose that fits your situation rather than the biggest number, and to follow your doctor’s advice if you have been diagnosed with a deficiency.
| Label strength | Where you often see it |
|---|---|
| 2.4 to 25 mcg | Multivitamins and some B complex products |
| 100 to 500 mcg | Lower-strength single B12 products |
| 1,000 mcg (1 mg) | The most common single-ingredient strength |
| 5,000 mcg | High strength, usually for use on advice |
Note that 1 mg and 1,000 mcg are the same amount, so a product labelled 1 mg, such as the cherry flavoured methylcobalamin sublingual, contains 1,000 mcg.
Tablets, lozenges or a B complex
- Swallowable tablets and capsules: simple and usually inexpensive.
- Lozenges and sublingual tablets: dissolve in the mouth. Many people like them because they are easy to take, although NIH ODS notes that sublingual forms have not been shown to work better than tablets you swallow.
- Liquids and drops: flexible doses, useful for people who dislike pills.
- B complex: contains B12 together with other B vitamins such as B6 and folate. Products like Paradise Herbs Earth’s Blend B-Complex suit people who want several B vitamins in one product.
- Multivitamins: many contain a small amount of B12 alongside other nutrients; see the multivitamins range.
If you are vegan, check that the capsule shell and other ingredients are plant-based. Many lozenges contain sweeteners or flavourings, which are listed on the label.
Safety and interactions
B12 is considered low risk, but a few points are worth knowing. Taking large amounts of folic acid can hide one sign of B12 deficiency in a blood test while nerve damage continues, which is one reason to see a doctor rather than self-treat if you suspect a deficiency. Some medicines reduce B12 absorption, as mentioned above. Always tell your doctor or pharmacist about every supplement you take.
If you also take vitamin D, the guide to choosing a vitamin D supplement explains the doses and upper limits for that vitamin, which work very differently from B12. Other single vitamins are listed in the vitamins category.
Quick checklist
- Check whether you are in a group more likely to be low in B12.
- See a doctor if you have symptoms or suspect a deficiency.
- Any common form is fine for most people; choose by price and format.
- 1 mg equals 1,000 mcg.
- Add up B12 from multivitamins and B complex products as well.
- Check vegan status, sweeteners and flavourings on the label.
- Tell your doctor or pharmacist about supplements, especially if you take metformin or acid-reducing medicines.
Common questions
Is methylcobalamin better than cyanocobalamin?
According to NIH ODS, research has not shown that one form works better than another for most people. Both are widely used, and cyanocobalamin is usually the cheaper and more stable option.
Why are B12 doses so much higher than the daily recommendation?
Because only a small part of a large oral dose is absorbed. A 1,000 mcg tablet provides far less than 1,000 mcg to the body, which is why such strengths are common.
Do vegans need a B12 supplement?
B12 occurs naturally almost only in animal foods, so vegans need fortified foods or a supplement to get enough. A doctor, pharmacist or dietitian can advise on the right approach.
