6PDG deficiency affects less than 1% of the population, and studies suggest that there may be race variant involved in many of the reported cases.

The lack of synthesis of a specific protein on chromosome 1 has reduced a subject suffering from 6PGD deficiency from producing adequate amounts of the 6-phosphogluconate dehydrogenase enzyme.

6PGD catalyzes the reaction of 6-phosphogluconate to an unstable form of 3-keto-6-phosphogluconate, and yields a co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) as a byproduct.

[citation needed] The NADPH pathway (both 6PGD and G6PD reactions) is the only source of reductant to reduce glutathione in red blood cells.

[citation needed] People suffering from 6PGD or G6PD deficiency (or both) are at risk of hemolytic anemia in states of oxidative stress.

[citation needed] Diagnosis is difficult during haemolytic episodes since reticulocytes have increased levels of enzymes and may produce erroneously normal results.

Testing can be useful after a steady state is reached (about six weeks after the most recent episode of haemolysis), including a G6PD assay to confirm a diagnosis and G6PD spectrophotometry to detect the level of activity.