Last updated: October 2026
Most people in the UK get enough vitamin B12 from meat, fish, eggs and dairy. A supplement is worth considering if you’re vegan, older, on metformin or long-term acid-reducing medicines, or have had stomach surgery. Adults need about 1.5 micrograms a day. If you have symptoms, get a GP blood test before you start.
The short version: vegans need a reliable B12 source for life. Any common form works for most people. Pernicious anaemia needs injections, not shop tablets. If you have symptoms, get tested first, because supplements can hide a deficiency.
Who may need a B12 supplement?
The NHS lists meat, fish, milk, cheese, eggs and some fortified breakfast cereals as good sources of B12. The people who need to think about a supplement are those who eat little or no animal food, or whose bodies struggle to absorb it.
| Who | Why | What to ask your GP or pharmacist |
|---|---|---|
| Vegans, and vegetarians who eat little dairy or few eggs | B12 isn’t found naturally in plant foods. The NHS says vegans may need tablets for life | “Are fortified foods enough, or do I need a supplement?” |
| Older adults, especially over 60 | The NHS says pernicious anaemia is more common in women around 60, and 10 to 30% of older people may not absorb the B12 in food (US advice quoted by the Vegan Society) | “Should I have a B12 test?” |
| People taking metformin | The MHRA says low B12 may affect up to 1 in 10 users, more with higher doses and longer use | “Should my B12 be checked, and how often?” Don’t stop metformin on your own. |
| Long-term PPI or H2 blocker users | Less stomach acid means less B12 released from food. In a large US study, 2 or more years of PPIs was linked to 1.65 times the odds of deficiency | “Do I still need this medicine, and should my B12 be checked?” |
| After stomach or weight loss surgery | NICE lists gastrectomy, gastric bypass and sleeve gastrectomy as risk factors | “Do I need injections or high-dose tablets?” |
| Pernicious anaemia (autoimmune gastritis) | The stomach can’t absorb B12, so food and low-dose supplements aren’t enough | “How often do I need injections?” |
NICE also lists colchicine, pregabalin, topiramate, some epilepsy medicines, coeliac disease and nitrous oxide use. If you take acid-reducing medicines for reflux, see our guide to acid reflux at night. For where B12 fits with other nutrients as you age, see supplements for men over 40 and 50 and supplements for women over 40.
Pernicious anaemia: injections, not shop tablets
The NHS says pernicious anaemia is the most common cause of B12 deficiency in the UK. NICE now calls it autoimmune gastritis: the immune system damages the stomach cells that make intrinsic factor, which you need to absorb B12.
The NHS says that if low B12 is caused by a stomach or bowel problem or surgery, you won’t absorb enough from food or low-dose supplements (10 to 100 micrograms). Treatment is usually hydroxocobalamin injections, every other day at first, then every 2 to 3 months for life, or high-dose 1,000 microgram tablets if you can’t have injections. NICE recommends lifelong injections for autoimmune gastritis and after total gastrectomy.
Cyanocobalamin vs methylcobalamin, tablets vs sprays
| Form | What it is | The honest verdict |
|---|---|---|
| Cyanocobalamin | A stable, manufactured form used in NHS tablets, fortified foods and many supplements | Works for most people, and it’s the form NHS tablets use |
| Methylcobalamin | One of the two active forms your cells use | Works too, but there’s no good evidence it’s better for most people |
| Adenosylcobalamin | The other active form in your cells | NICE lists it as an acceptable supplement form |
| Hydroxocobalamin | The form in NHS injections | Preferred to cyanocobalamin for injections in the UK |
NICE advises choosing a supplement with cyanocobalamin, methylcobalamin or adenosylcobalamin, as some products don’t contain enough, or the right type, to work. A 2017 review found every form is broken down to the same core molecule and rebuilt into the two active forms, whatever you swallow. Its authors, one of whom worked for a supplement company, favoured the “natural” forms but agreed most people would likely find all forms work about the same. Methylcobalamin is fine, but you don’t need to pay more for it.
Tablets, under-the-tongue tablets, sprays and injections
The NHS says there’s no noticeable difference in how much B12 you absorb from tablets, under-the-tongue tablets, capsules, mouth sprays or drops. In one small trial, 500 micrograms worked equally well under the tongue or swallowed. A 2018 Cochrane review found 1,000 to 2,000 micrograms a day by mouth raised blood levels as well as injections, though the evidence was low quality. A spray is simply handy if you dislike tablets. Injections are for people who can’t absorb B12 or have severe symptoms, and come from your GP.
How much B12 per day?
| Situation | Amount | Source |
|---|---|---|
| What adults (19 to 64) need from food | About 1.5 micrograms a day | NHS |
| Vegans, fortified foods | At least 3 micrograms a day, from fortified foods eaten 2 or 3 times a day | Vegan Society |
| Vegans, daily supplement | At least 10 micrograms a day | Vegan Society |
| Vegans, weekly supplement | At least 2,000 micrograms once a week | Vegan Society |
| Diet-related deficiency (prescribed) | 50 to 150 micrograms once a day | NHS |
| Deficiency not caused by diet, if injections aren’t possible | 1,000 to 2,000 micrograms once or twice a day | NHS |
| Upper amount from supplements | 2mg (2,000 micrograms) a day or less is unlikely to cause harm | NHS |
Shop supplements range from 10 to 1,000 micrograms, which looks huge next to 1.5 micrograms, because only a small share of a large dose is absorbed. In a Dutch trial, older people with mild deficiency needed 647 to 1,032 micrograms a day to bring blood markers back to normal. Many multivitamins contain B12 too, so check labels if you take more than one product.
How to take it and how long until you feel better
- Prescribed tablets: the NHS says swallow them whole with water, ideally on an empty stomach, at least 2 hours after eating and 30 minutes before your next meal.
- Shop supplements: follow the pack. The Vegan Society suggests chewing tablets or letting them dissolve in your mouth.
- Daily or weekly: pick whichever you’ll stick to. Taking it with breakfast is easy to remember.
How long to work: NICE says symptoms could start to improve within 2 weeks but may take up to 3 months, longer to clear completely, and can feel worse at first. Your GP should review you at about 3 months.
How long to take it: you may be able to stop once levels are normal and the cause is fixed. If you’re vegan, or can’t absorb B12, you may need it for life.
Get tested before you start
If you have symptoms, see your GP before you buy a supplement. Our guide to vitamin B12 deficiency symptoms covers the signs.
NICE tells doctors to take blood for B12 tests before starting treatment, and warns that shop supplements can raise test results without fully treating a deficiency. That can hide the cause, such as pernicious anaemia, which needs lifelong treatment. If you already take B12, tell your GP. A total B12 under 180 nanograms per litre confirms deficiency, and 180 to 350 is a grey area that may need a further test.
See your GP promptly if you have numbness, balance problems or vision changes, as the NHS says nerve problems from low B12 can sometimes be permanent. See pins and needles for other causes.
Does B12 give you energy?
Only if you’re low in it. These are the authorised health claims for B12 in Great Britain:
- 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.
The NHS is clear that B12 supplements will only improve tiredness and lack of energy if they’re caused by low B12 levels. Topping up when your levels are normal, including with private “booster” injections, is unlikely to give you more energy.
Tiredness has many causes. See why am I always tired?, iron deficiency symptoms, brain fog and the best supplements for energy. If your GP also finds low iron, see iron tablets.
Safety, side effects and medicines
- Dose: the NHS says 2mg (2,000 micrograms) or less a day from supplements is unlikely to cause harm.
- Side effects: most people have none. B12 contains cobalt, so people allergic to cobalt can react. Call 999 if your lips, tongue or throat swell or you struggle to breathe.
- Medicines: metformin, PPIs such as omeprazole, H2 blockers and antacids can reduce how much B12 you absorb, so tell your pharmacist. The MHRA says don’t stop metformin without talking to your doctor.
- Pregnancy and breastfeeding: the NHS says cyanocobalamin is safe, but you don’t usually need B12 supplements unless your doctor advises it. If you’re vegan, ask your midwife.
The NHS lists a sore red tongue, sometimes with mouth ulcers, as a sign of low B12: see mouth ulcers. For how B12 compares with B6, see vitamin B6.
Does Evopure sell vitamin B12?
No. Evopure doesn’t make a B12 supplement, and if you’re low you need the dose your GP recommends.
Our Magnesium Glycinate Sleep Complex is a vegan, berry-flavoured bedtime drink with magnesium bisglycinate and citrate. Magnesium contributes to a reduction of tiredness and fatigue. See magnesium for energy. Our products are for adults only, and we don’t recommend them during pregnancy or breastfeeding.
FAQs
Do I need a vitamin B12 supplement?
Most people who eat meat, fish, eggs or dairy get enough. Vegans usually need fortified foods or a supplement. If you’re older, take metformin or long-term acid-reducing medicines, or have had stomach surgery, ask your GP about a test.
Is methylcobalamin better than cyanocobalamin?
There’s no good evidence that it is for most people. Both become the same core molecule in the body, and NICE lists both as acceptable supplement forms.
How much B12 should I take a day?
Adults need about 1.5 micrograms a day. The Vegan Society suggests at least 10 micrograms a day or 2,000 micrograms a week for vegans. The NHS says 2mg or less a day from supplements is unlikely to cause harm.
Are B12 sprays better than tablets?
No. The NHS says there’s no noticeable difference in absorption between tablets, capsules, mouth sprays and drops. Choose the one you’ll take regularly.
How long do B12 tablets take to work?
The NHS says it may take a few weeks for levels and symptoms such as tiredness to improve. NICE says symptoms may start to improve within 2 weeks but can take up to 3 months.
Can you take too much B12?
The NHS says 2mg or less a day from supplements is unlikely to cause harm. Most people have no side effects, but people allergic to cobalt can react.
Should I get a blood test before taking B12?
Yes, if you have symptoms. Supplements can raise your result without fully treating a deficiency, which can hide the cause.
Sources
- NHS. B vitamins and folic acid; vitamin B12 or folate deficiency anaemia, its vitamin B12 deficiency anaemia: causes and treatment.
- NHS. Cyanocobalamin (dosage, common questions, side effects, pregnancy).
- NICE. Vitamin B12 deficiency in over 16s: diagnosis and management (NG239), 2024.
- MHRA. Metformin and reduced vitamin B12 levels, 2022.
- The Vegan Society. What every vegan should know about vitamin B12.
- Wang H et al. Oral vs intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane, 2018. PMID 29543316. Paul C, Brady DM. Comparative bioavailability of B12 forms. Integr Med, 2017. PMID 28223907. Sharabi A et al. Sublingual vs oral B12. Br J Clin Pharmacol, 2003. PMID 14616423. Eussen SJ et al. Oral cyanocobalamin dose-finding trial in older people. Arch Intern Med, 2005. PMID 15911731. Lam JR et al. PPI and H2 blocker use and B12 deficiency. JAMA, 2013. PMID 24327038.
This guide is general information, not medical advice. Evopure does not sell a vitamin B12 supplement. Evopure makes the Magnesium Glycinate Sleep Complex.
