Glucose-6-phosphate dehydrogenase (G6PD)

What it measures

Measures the activity of G6PD, an enzyme that protects red cells from oxidative damage. Deficiency causes hemolysis after certain drugs, infections or fava beans, and neonatal jaundice.

Specimen and preparation

• Specimen: Whole blood (EDTA or heparin)
• Tube: Lavender top
• Preparation: Avoid testing during or just after a hemolytic episode; young red cells have higher activity and may mask deficiency. Repeat 2–3 months later if normal.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Reticulocytosis or recent hemolysis (young cells)
• Recent transfusion

Causes of low values

• Inherited G6PD deficiency (X-linked; mostly males)
• Heterozygous females may show intermediate activity

Method

Fluorescent spot test (screen) or quantitative spectrophotometric assay (U/g Hb)

Good to know

Test before primaquine, tafenoquine, dapsone or rasburicase. Units and cut-offs vary by method.

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