A G6PD Screen (Glucose-6-Phosphate Dehydrogenase) is a blood test that checks whether you have enough of the G6PD enzyme in your red blood cells. G6PD helps protect red blood cells from “oxidative stress” (cell damage caused by certain medications, infections, or foods). If you have G6PD enzyme deficiency, your red blood cells can break down too quickly (called hemolysis), which can lead to hemolytic anemia.

This test is commonly used as a screening test—it identifies people who may have low G6PD activity. Some laboratories use a qualitative “screen” first and may follow it with a quantitative G6PD level (a numeric enzyme activity measurement) to confirm results or assess severity.

What the results generally mean:

• Normal/negative screen: G6PD activity is likely sufficient, and G6PD deficiency is less likely. However, in certain situations (especially during or soon after an episode of hemolysis), the result can appear normal because younger red blood cells may have higher G6PD activity.

• Abnormal/positive screen (low activity): Suggests G6PD deficiency. This increases the risk of hemolytic anemia when exposed to specific triggers (for example, certain antibiotics, antimalarial drugs, or fava beans—often called favism).

Important timing note: If testing is done during active hemolysis or shortly after a transfusion, results can be misleading. Your clinician may recommend repeat testing or a quantitative confirmatory test once blood counts stabilize.

Doctors often order a G6PD screen when there is concern for red blood cell breakdown (hemolysis) or before prescribing medications known to trigger hemolysis in people with G6PD deficiency.

This test is commonly done if you have symptoms of hemolytic anemia, such as:

• Sudden fatigue or weakness

• Pale skin

• Shortness of breath

• Rapid heart rate

• Yellowing of the skin or eyes (jaundice)

• Dark or tea-colored urine

• Back or abdominal pain (sometimes)

It may be ordered after exposure to common triggers, including:

• Certain medications (for example some sulfa antibiotics, dapsone, primaquine and related antimalarials, rasburicase, and others—your clinician/pharmacist can review your specific list)

• Foods such as fava beans (favism)

• Chemicals such as naphthalene (mothballs)

• Acute infections (infections themselves can trigger oxidative stress and hemolysis)

It is also often done for risk-based screening, such as:

• Newborns with significant jaundice or unexplained anemia

• People with a family history of G6PD deficiency or episodes of hemolytic anemia

• Individuals from populations where G6PD deficiency is more common (including African, Mediterranean, Middle Eastern, and parts of Asian ancestry)

• Before starting certain high-risk treatments (e.g., rasburicase) where G6PD deficiency can lead to severe complications

Because G6PD deficiency is inherited (X-linked), it is more often fully expressed in males, though females can also have deficiency or intermediate enzyme activity and may still be at risk.

• G6PD deficiency (glucose-6-phosphate dehydrogenase deficiency)
• Hemolytic anemia (especially oxidative or drug-induced hemolysis)
• Acute hemolytic crisis after medication exposure, infection, or favism
• Neonatal jaundice related to increased red blood cell breakdown
• Hyperbilirubinemia (elevated bilirubin from hemolysis)
• Favism (hemolysis triggered by fava beans)

• Preventing medication-related complications by identifying G6PD enzyme deficiency before starting certain drugs
• Reducing risk of hemolytic anemia through trigger avoidance and safer treatment choices
• Supporting newborn health by evaluating causes of significant jaundice and guiding monitoring
• Personalized care and family planning by clarifying inherited risk (including screening of family members when appropriate)
• Improving overall safety during illness by recognizing higher hemolysis risk during infections and managing promptly