G6PD Blood Test: Normal Ranges, Causes & What Your Results Mean

What Is G6PD?

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme found in all cells, but it is particularly important in red blood cells. It catalyses the first step of the pentose phosphate pathway, generating NADPH - a molecule that protects red blood cells from oxidative damage by maintaining glutathione in its reduced (active) form.

G6PD deficiency is the most common enzyme deficiency worldwide, affecting approximately 400 million people. It is an X-linked genetic condition, meaning it predominantly affects males, though carrier females can also show symptoms. The deficiency is most prevalent in populations from Africa, the Mediterranean, the Middle East, and Southeast Asia - regions where malaria is or was endemic, as G6PD deficiency confers partial protection against malaria.

People with G6PD deficiency are usually asymptomatic until exposed to an oxidative trigger (certain medications, fava beans, infections), which can cause acute haemolytic anaemia - the rapid destruction of red blood cells.

Why Is G6PD Tested?

• Pre-medication screening - many common drugs (primaquine, dapsone, rasburicase, high-dose aspirin) can trigger haemolysis in G6PD-deficient individuals
• Unexplained haemolytic anaemia - G6PD deficiency should be considered in any patient with acute haemolysis, especially males of African, Mediterranean, or Asian descent
• Neonatal jaundice - G6PD deficiency is a significant cause of severe neonatal jaundice
• Family screening - if a family member is affected, screening other males is recommended
• Favism investigation - haemolysis after eating fava beans (broad beans)
• Pre-surgical planning - knowledge of G6PD status helps anaesthetists avoid triggering drugs

Normal Ranges

Note: G6PD levels can appear falsely normal during or shortly after a haemolytic crisis (because the oldest, most deficient cells have been destroyed). Retesting 2–3 months after an acute episode gives a more accurate result.

What Does G6PD Deficiency Mean?

• Risk of drug-induced haemolysis - antimalarials (primaquine), antibiotics (sulfonamides, nitrofurantoin), and analgesics can trigger red cell destruction
• Favism - fava beans contain oxidants (vicine, convicine) that cause acute haemolysis in deficient individuals
• Infection-triggered haemolysis - bacterial and viral infections increase oxidative stress, potentially causing haemolysis
• Neonatal hyperbilirubinaemia - G6PD deficiency is the most common enzymatic cause of severe newborn jaundice worldwide
• Chronic non-spherocytic haemolytic anaemia - rare severe variants cause ongoing haemolysis even without triggers

What Do High G6PD Levels Mean?

• Usually not clinically significant - elevated G6PD is uncommon but can occur with reticulocytosis (high proportion of young red cells after blood loss or haemolysis)
• Hyperthyroidism - may mildly elevate G6PD activity

How to Manage G6PD Deficiency

• Carry a medical alert card - ensure all healthcare providers know your G6PD status before prescribing medications
• Avoid trigger medications - the British National Formulary (BNF) lists drugs to avoid; always check before starting new medicines
• Avoid fava beans - if you have a severe variant (common in Mediterranean populations)
• Treat infections promptly - infections are the most common trigger of haemolytic crises
• Ensure adequate hydration - during a haemolytic episode, hydration supports kidney function
• Genetic counselling — X-linked inheritance means carrier mothers have a 50% chance of passing deficiency to sons

When Should You Get Tested?

• You have a family history of G6PD deficiency
• You are of African, Mediterranean, Middle Eastern, or Southeast Asian descent and experiencing unexplained anaemia
• You developed jaundice or dark urine after taking a new medication or eating fava beans
• Before starting medications known to cause haemolysis in G6PD-deficient patients
• Newborn screening if there is a family history or unexplained neonatal jaundice

Which Lola Health Tests Include G6PD?

G6PD enzyme activity is available as an add-on biomarker with any Lola Health blood test. It is a one-time test — your G6PD status does not change over your lifetime (though results should not be tested during an active haemolytic episode).