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Vitamin B12 deficiency can cause anaemia and affect the nerves and brain. Symptoms usually develop gradually, and some problems can be permanent if the condition is not treated. See a doctor for a blood test rather than guessing.
What are the symptoms?
- Tiredness or weakness
- Breathlessness and palpitations
- Headaches
- A sore or red tongue, or mouth ulcers
- Reduced appetite and indigestion
- Numbness and pins and needles
- Muscle weakness and balance problems
- Memory problems or mood changes
Which foods contain vitamin B12?
Meat, fish, milk, dairy products and eggs contain vitamin B12. Vegetarians and vegans can look for fortified foods, such as some breakfast cereals, yeast extracts and soy products.
How is it treated?
Treatment depends on the cause. When it is diet related, tablets or injections may be used. When the body cannot absorb B12, such as in pernicious anaemia, regular injections are usually needed for life. Blood tests check that treatment is working.
When should I see a doctor?
See a doctor if you have any of these symptoms. The longer it goes untreated, the greater the risk of lasting damage.
Doses vary, so follow your prescriber, pharmacist and the medicine label. In an emergency, call triple zero (000). For a possible overdose, call the Poisons Information Centre on 13 11 26.
Source: NHS: Symptoms and NHS: Treatment. General education does not replace individual medical advice. Updated November 2026.
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