Vitamin B12 and Folate Deficiency

🧭 When to suspect (vitamin B12 and folate deficiency)

Vitamin B12 and folate are both needed for DNA synthesis and red-cell production, and B12 is additionally essential for myelin integrity – which is why deficiency can produce haematological problems (a macrocytic anaemia), neurological problems, or both. The two deficiencies frequently coexist, so folate and B12 are always checked and interpreted together.

The single most useful change in practice is this: do not wait for anaemia. B12 deficiency can present with neurological symptoms and a completely normal blood count, so a normal FBC never excludes it. Current guidance recommends offering a B12 test to anyone with at least one symptom or sign (such as unexplained fatigue, paraesthesia, balance problems, glossitis, cognitive ‘brain fog’, or visual disturbance) and at least one risk factor; use clinical judgement where there are symptoms but no obvious risk factor.

Raise suspicion particularly with a vegan or restricted diet, autoimmune gastritis (the cause historically called pernicious anaemia), previous gastric or bariatric surgery or terminal ileal resection, coeliac or other autoimmune disease, long-term metformin or proton pump inhibitors, recreational nitrous oxide use, and in pregnancy where anaemia is not responding to iron.

Source: NICE NG239 · MHRA Drug Safety Update