Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency in humans, affecting more than 400 million people globally. It is inherited as an X-linked recessive disorder. Deficiency of the G6PD enzyme can make the red cells vulnerable to oxidative damage and liable to haemolysis, the rupturing of red blood cells and the release of their contents into surrounding fluid.

Most individuals with the G6PD defect are asymptomatic and unaware of their status. Most people with G6PD deficiency have a normal life expectancy despite a predisposition to neonatal jaundice and sensitivity to certain drugs.