G6PD deficiency and the chromosome

The G6PD gene provides instructions for an enzyme that helps protect red blood cells. When the enzyme activity is low, an infection, certain medicines, or some foods may trigger haemolysis, meaning red blood cells are removed faster than the body replaces them. The gene is on the X chromosome, so family patterns can differ between people.

Possible signs include yellowing of the skin or eyes, unusual tiredness, breathlessness, a fast heartbeat or dark urine. A symptom such as [Dark Urine](/symptoms/dark-urine/) needs assessment in context; it does not by itself identify the cause.

Tell every clinician and pharmacist that G6PD deficiency is possible or confirmed before starting a medicine. Keep a current list of medicines and products, and ask whether an infection or new food could have triggered symptoms. Diagnosis may involve a [Blood Test](/treatments/diagnostics-and-screening/blood-test/) that measures enzyme activity and checks blood cells. Testing during or soon after haemolysis may need careful timing because the result can be misleading.

Seek urgent medical help for rapidly worsening weakness, severe breathlessness, fainting, confusion, a racing heartbeat, or very dark urine with yellow skin or eyes. These can signal significant red-cell breakdown or anaemia. A baby with marked [Pale Skin](/symptoms/pale-skin/) or poor feeding should be assessed promptly.

Ask which gene result or enzyme level was found, which medicines and household products to avoid, whether relatives should be tested, and when repeat testing would be useful.