How is G6PD deficiency tested?

The test checks how much G6PD enzyme is available to protect red blood cells from oxidative stress. A low activity result can support the diagnosis, while the result must be interpreted with the person’s symptoms, blood count, family history, and recent treatment. During or soon after a haemolytic episode, many older red blood cells have already been removed, so timing can affect the result. A clinician may recommend repeat testing when the result does not fit the clinical picture.

Tell the clinician about recent fever, jaundice, dark urine, transfusion, and medicines. Mention any known family diagnosis and ancestry that may be relevant to inherited risk. Do not delay urgent assessment while waiting for a planned test. The procedure is a routine blood draw; learn more about [Blood Test](/treatments/diagnostics-and-screening/blood-test/).

Seek urgent care for rapidly worsening weakness, breathlessness, fainting, yellow eyes, very dark urine, or severe pallor. These symptoms can indicate active red blood cell breakdown and need clinical assessment even if a previous test was normal. Related information is available for [Dark Urine](/symptoms/dark-urine/) and [Pale Skin](/symptoms/pale-skin/).

Ask whether the test should be repeated, how recent illness or transfusion affects interpretation, and whether relatives should be offered testing. Ask when your result should be shown before prescribing new medicines.