How effective is blood test for G6PD deficiency?

The test measures how well red blood cells make G6PD, an enzyme that helps protect them from oxidative stress. A low activity result supports the diagnosis. During or soon after rapid red-cell breakdown, the blood may contain younger cells with more enzyme activity, which can make a deficiency look less clear. A recent blood transfusion can also influence the sample. The clinician will interpret the result with your symptoms, medicines, infections and family background.

Tell the clinician about jaundice, dark urine, unusual tiredness, recent infection, new medicines, fava beans and any transfusion. If the result is uncertain, ask whether testing should be repeated when you are well or whether specialist advice is needed. Keep a written list of medicines and mention the possible diagnosis before taking a new prescription or supplement.

Get urgent help for yellowing of the eyes, cola-coloured urine, severe weakness, breathlessness, fainting, confusion or a fast heartbeat. These can occur when red blood cells are breaking down quickly and need prompt assessment. Do not wait for a routine test appointment if symptoms are sudden or severe.

Ask whether the sample was taken during a haemolytic episode, whether a transfusion could affect it, and whether repeat enzyme testing or genetic assessment is appropriate. Ask which medicines and foods you should avoid while the diagnosis is being clarified and what warning signs require emergency care.