G6PD (glucose-6-phosphate dehydrogenase)
An enzyme that protects red blood cells from oxidative stress. When it is deficient — a common inherited condition, especially around the Mediterranean, Africa and Asia — certain triggers (fava beans, some medicines, infections) can make red cells break down, causing sudden anaemia and jaundice.
What it measures
Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme inside red blood cells that produces a molecule protecting them from oxidative damage. G6PD deficiency is the commonest human enzyme disorder, inherited on the X chromosome (so it mainly affects men), and is especially common in people of Mediterranean, Middle Eastern, African and Southeast Asian descent — thought to have persisted because it offers some protection against malaria. Most of the time people with it are completely well, because red cells are only stressed when exposed to specific triggers. But when triggered, the protection fails and red cells break apart (haemolysis), causing a sudden drop in haemoglobin, jaundice and dark urine. The classic triggers are fava (broad) beans — giving the condition its old name 'favism' — certain medicines (some antibiotics, antimalarials and others), and infections. Diagnosis is by measuring the enzyme level, ideally done a few weeks after an episode has settled, because during active haemolysis the youngest red cells (with more enzyme) can give a falsely normal result.
What a high value can mean
- Not typically a clinical concern — a normal or high enzyme level is reassuring; the important direction is a low (deficient) level.
- After a recent haemolytic episode — new young red cells can raise the reading, sometimes masking deficiency (hence testing later).
What a low value can mean
- G6PD deficiency — the meaningful result; red cells are vulnerable to oxidative stress.
- Risk when triggered — fava beans, certain medicines (some antibiotics, antimalarials), and infections can cause haemolysis (anaemia, jaundice, dark urine).
- In newborns — can cause prolonged or severe jaundice.
When to discuss with a doctor
Knowing about G6PD deficiency matters mainly for prevention: someone with it should avoid fava beans and be cautious with specific medicines that can trigger haemolysis, and doctors and pharmacists check drug choices against it. It is worth testing in someone who has had unexplained haemolysis (sudden anaemia with jaundice and dark urine, especially after fava beans, a new medicine or an infection), in a newborn with severe jaundice, and for family screening. Testing is best done when well, a few weeks after any episode, to avoid a falsely normal result. If a trigger causes haemolysis, avoiding it and supportive care usually allow recovery. Mediora.AI shows G6PD alongside the haemolysis markers (haptoglobin, LDH, reticulocytes, bilirubin) so the pattern is read together; the interpretation belongs with your doctor.