What causes vitamin B12 deficiency?

B12 comes mainly from animal foods and fortified products. A vegan diet without reliable fortified foods or supplements may provide too little. Absorption can also fall when the stomach or small intestine is affected. Coeliac disease can damage the bowel lining and reduce the amount of B12 absorbed. Stomach surgery, some bowel disorders, and autoimmune loss of a stomach protein needed for absorption are other possibilities.

Some medicines, including certain medicines for diabetes or excess stomach acid, can reduce absorption over time. Symptoms may include tiredness, a sore tongue, pale skin, pins and needles, balance changes, or memory difficulties. These symptoms have several possible causes, so testing is needed rather than guessing from symptoms alone.

Arrange a medical assessment if symptoms persist or you have a diet, digestive condition, or medicine that raises concern. A clinician may review your food intake and medicines and request blood tests for B12 and related blood changes. Treatment depends on the cause: dietary changes or tablets may help some people, while injections may be needed when absorption is poor. Do not stop a prescribed medicine without advice.

Seek prompt medical care for new or worsening weakness, trouble walking, marked confusion, or increasing numbness, because prolonged deficiency can affect nerves. Seek urgent help for sudden severe confusion, collapse, or difficulty speaking. Early assessment helps identify a reversible cause and reduces the chance of lasting nerve problems.

Ask whether your symptoms and blood results fit B12 deficiency, whether coeliac disease or another absorption problem should be considered, and whether your current medicines or diet could contribute. You can also ask how long treatment is expected to continue and when your blood tests should be repeated.