G6PD and malaria: Because of selective pressure, G6PD mutations resulting in reduced erythrocytic G6PD activity levels are typically frequent in malaria-endemic regions.1 Thailand and southeast Asia are no exceptions, with G6PD deficiency reaching over 15% prevalence in certain populations.2,3 It is, therefore, critical to diagnose whether a patient is G6PD-deficient before administering an 8-aminoquinoline drug for radical cure of P. vivax malaria.