Vitamin B12 Deficiency

Low B12 can cause tiredness, anaemia, tingling, memory problems and a sore tongue. Common causes include a vegan diet, some medicines and pernicious anaemia.

Treatment options

Ratings show how strong the research is.

• Strong evidenceB12 injectionsNeeded for severe deficiency, nerve symptoms or pernicious anaemia. A loading course, then every 2 to 3 months.
• Strong evidenceTreat the causeFor example diet, metformin or acid-reducing medicines, coeliac disease or pernicious anaemia.
• Strong evidenceLifelong treatment if neededPernicious anaemia and some causes need B12 for life.
• Moderate evidenceHigh-dose B12 tabletsFor most people, high-dose tablets work as well as injections (Cochrane review). Taken daily.
• Limited evidenceNasal sprays and patchesLittle evidence. Not recommended.

What you can do

• Vegans and vegetarians: use fortified foods or a supplement.
• Don’t stop treatment just because symptoms improve.

See your GP if

• Tingling, numbness, unsteadiness or memory changes
• You’re pregnant, vegan or on metformin long-term
• Symptoms return

See a doctor urgently for new weakness, falls, or trouble walking.

Evidence and more information

• Healthdirect: Vitamin B12
• Cochrane: Oral vs injected B12

Reviewed October 2026. General education, not personal medical advice. Treatment depends on your situation, so talk to your GP or pharmacist.

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