GSR and G6PD deficiency: G6PD deficiency is the most common enzyme deficiency in humans and affects over 400 million people worldwide.4 The glutathione pathway is paramount to antioxidant defense and G6PD-deficient cells do not cope well with oxidative damage.5 Normal values of G6PD, 6-phosphogluconate dehydrogenase (6PGD) and glutathione reductase (GR) have been determined in normocytes, reticulocytes, newborn cord erythrocytes and leukocytes.6