G6PD test: what the result means

G6PD is an enzyme that every cell needs, but it is especially important in red blood cells (erythrocytes) — it helps to protect them from damage caused by certain substances and from breaking down earlier than they should (haemolysis). The gene that codes for this enzyme is on the X chromosome, so G6PD deficiency is an inherited condition that appears more often in men. When the activity of the enzyme is reduced, red blood cells become more sensitive to oxidative stress — this can be brought on by infections, certain foods (for example fava beans, also called broad beans) or certain groups of medicines. Because of that, a haemolytic episode can bring tiredness, pale or yellowish skin, dark urine, a fast heartbeat and breathlessness. According to MedlinePlus, normal test values depend on the laboratory and the method used, so there is no general numerical interval — the result is assessed against the result sheet of the particular laboratory, together with the clinical picture.

• When a newborn has prolonged or severe jaundice
• When haemolytic anaemia is suspected — a fast breakdown of red blood cells with tiredness, paleness or jaundice
• Before certain medicines are prescribed, if there are risk factors or a family history of G6PD deficiency
• After a haemolytic episode linked to an infection, a certain food or medicines, in order to establish the cause
• When there are known cases of G6PD deficiency in the family

According to MedlinePlus, normal G6PD test values depend on the particular laboratory and the method used, so there is no general numerical interval — and that is why no single figure is given here. You will find the exact limits and the interpretation on the result sheet of your own laboratory, together with your doctor's explanation; the result is assessed together with the clinical picture. If the figures on the sheet are unfamiliar, see how to read blood test results.

Reduced G6PD activity

Reduced G6PD activity means an inherited deficiency of the enzyme — most often in men, because the gene is on the X chromosome. It increases the risk that certain circumstances (an infection, a certain food or medicines) will bring on the breakdown of red blood cells (haemolysis). MedlinePlus does not give a specific numerical interval — the result is assessed according to the method the laboratory uses.

What can lie behind reduced activity

• An inherited G6PD deficiency (a mutation in a gene on the X chromosome)
• Fava beans (broad beans) — a haemolytic episode they bring on is called favism
• Viral infections
• Bacterial infections
• Certain antibiotics
• Antimalarial medicines
• Non-steroidal anti-inflammatory drugs (NSAIDs), for example ibuprofen and aspirin
• During a haemolytic episode the result can be unreliable, so a doctor may suggest repeating the test in a few weeks (MedlinePlus)

Possible symptoms

• Tiredness
• Pale skin or jaundice (yellowing of the skin and of the whites of the eyes)
• A fast heartbeat
• Breathlessness
• Dark or yellow-orange urine

What to discuss with a doctor

• Which factors (an infection, a certain food, a group of medicines) could have brought on the haemolytic episode
• Whether substances that cause oxidative stress need to be avoided in future — this is discussed with a doctor
• In newborns — whether the jaundice needs additional monitoring or treatment
• Family history and, if relevant, testing of close relatives

Related tests

• Haemoglobin
• Bilirubin
• Reticulocytes
• LDH
• Red blood cells
• Full blood count