G6PD deficiency in females

One X chromosome may carry a G6PD gene change while the other does not. Cells do not always use both X chromosomes equally, so enzyme activity can vary from one female to another. Some have no symptoms, while others can develop haemolysis after an infection, certain medicines or another trigger.

When red cells break down quickly, a person may develop yellow skin or eyes, tiredness, breathlessness, a fast heartbeat or [Pale Skin](/symptoms/pale-skin/). A symptom is a reason for assessment, not proof of G6PD deficiency.

Mention possible or confirmed G6PD deficiency before taking a new medicine, including medicines prescribed by another service. Ask about products used during pregnancy, menstruation or an infection. A [Blood Test](/treatments/diagnostics-and-screening/blood-test/) can help measure enzyme activity, but the timing and clinical context matter.

Get urgent medical attention for sudden weakness, fainting, confusion, severe breathlessness, a racing heartbeat, or [Dark Urine](/symptoms/dark-urine/) together with yellowing. Mention pregnancy or recent childbirth, if relevant, because the care team will need the full context.

Ask whether your enzyme activity is reduced, which triggers and medicines matter, whether relatives or children should be tested, and whether testing should be repeated after an episode.