“B12 supplements prevent and treat B12 deficiency.”
B12 supplements, as tablets or shots, reliably prevent and treat B12 deficiency.
If you are at risk of low B12, a supplement or fortified foods are a reliable way to prevent deficiency, and treatment works when levels are low. If you are not at risk, there is no need to take extra.
If you are vegan, over 50, take metformin or an acid-reducing medicine, or have had stomach surgery, ask your doctor whether you should take B12 or have your level checked.
Safety note: High-dose folic acid can hide the anemia of B12 deficiency while nerve damage continues, which is why doctors check B12 before treating low folate.
Talk to a healthcare professional if: you have numbness, pins and needles, balance problems, memory trouble, a sore tongue or tiredness you cannot explain, especially if you are in one of the higher-risk groups above.
B12 replacement is standard care in national guidelines, and trials show that both high-dose tablets and injections bring low B12 levels back to normal. The best form depends on the cause of the deficiency, not on whether B12 works.
B12 supplements, as tablets or shots, reliably prevent and treat B12 deficiency. That is why B12 replacement is standard care for people who are low or at high risk.
A Cochrane review of 3 trials in 153 people with B12 deficiency found that 1,000 micrograms a day by mouth raised B12 levels about as well as injections, at lower cost; the evidence for that comparison was rated low quality because the trials were small. UK national guidance offers either tablets or injections depending on the cause, and lifelong injections when the body cannot absorb B12 normally, such as with autoimmune gastritis (often called pernicious anemia) or after removal of the stomach. The stomach makes a protein (intrinsic factor) that the body needs to absorb B12 well. When the cause is a medicine such as metformin, guidance says tablets or injections can be used while the medicine is taken.
Who is most likely to need a B12 supplement?
People who eat little or no animal food (vegans and many vegetarians) and do not use fortified foods, many adults over 50, people taking metformin or long-term stomach-acid medicines (proton pump inhibitors or H2 blockers), and people with pernicious anemia, celiac or Crohn disease, or past stomach or weight-loss surgery. Some of these groups need a specific treatment plan, such as injections, not just a standard supplement.
- National Institute for Health and Care Excellence (NICE). Vitamin B12 deficiency in over 16s: diagnosis and management. NICE guideline NG239. Published 6 March 2024
- Wang H, Li L, Qin LL, Song Y, Vidal-Alaball J, Liu TH. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database of Systematic Reviews. 2018;(3):CD004655. DOI: 10.1002/14651858.CD004655.pub3. PMID: 29543316. PMCID: PMC6494183
- MedlinePlus, National Library of Medicine. Vitamin B12. Medical Encyclopedia. Review date January 21, 2025
- NHS. Vitamin B12 or folate deficiency anaemia: treatment. Page last reviewed 20 February 2023