Glucose-6-Phosphate Dehydrogenase, Serum or Red Blood Cell, Catalytic Concentration

What the Test Measures

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme found in red blood cells that helps shield them from harmful oxidative stress. This test quantifies how much enzyme activity is present, expressed as a catalytic concentration. Because the exact units and whether the sample is serum or red blood cells can vary by laboratory, your report will include the specific units and specimen used.

Why It Is Ordered

Doctors order a G6PD test when they suspect G6PD deficiency. This may happen after an episode of unexplained red blood cell destruction (hemolysis), when jaundice appears in a newborn, or before prescribing certain medications that can trigger hemolysis in people with the deficiency. It may also be part of an evaluation for a type of anemia.

How the Sample Is Collected

The test is usually performed on a blood sample drawn from a vein in your arm. Depending on the laboratory, the measurement may be done on serum or on red blood cells. No special preparation is typically required, though you should follow any instructions your care team provides.

What the Results Mean

Results are interpreted by comparing your enzyme activity to the laboratory's expected range. Lower-than-expected activity may suggest G6PD deficiency, while normal activity generally makes the deficiency less likely. Because results can be affected by recent hemolysis (which can falsely raise activity) and by the specific method used, your healthcare provider will interpret the result alongside your symptoms, history, and other tests. No single number should be read in isolation.