What causes pernicious anaemia?

Vitamin B12 needs a stomach-made protein called intrinsic factor before it can be absorbed in the small intestine. In pernicious anaemia, immune activity can reduce intrinsic factor or injure the cells that produce it. B12 is needed to make healthy red blood cells and support nerves, so a shortage may lead to tiredness, pale skin, breathlessness, a sore tongue, or pins and needles. Other causes of B12 deficiency, including restricted intake, stomach or bowel disorders, and some medicines, are different from pernicious anaemia, although they can produce similar symptoms.

Arrange a medical assessment if symptoms persist or you have risk factors such as previous stomach surgery or another autoimmune condition. A clinician may review your symptoms, examine you, and request blood tests for blood-cell changes, vitamin B12, and markers that support the diagnosis. Treatment commonly replaces B12, often by injection when absorption is impaired. Do not rely on iron supplements alone unless testing shows iron deficiency; iron deficiency anaemia has a different mechanism.

Seek urgent help for new weakness, trouble walking, confusion, chest pain, severe breathlessness, or fainting. Nerve symptoms can worsen if B12 deficiency is left untreated, so book a prompt appointment for continuing numbness, balance changes, marked fatigue, or a sore tongue.

Ask whether your results suggest pernicious anaemia or another cause of B12 deficiency, whether you need antibody testing, how B12 will be replaced, and how symptoms and blood tests will be monitored.