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G6PD deficiency


Red blood cells are needed to deliver oxygen from the lungs to other parts of the body. Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme that protects red blood cells. Some people do not have enough G6PD to protect their red blood cells. This condition is called “G6PD deficiency.”

People with G6PD deficiency are at higher risk for red blood cell destruction. This is especially true after they are exposed to certain “triggers” (certain medicines and some foods). As a result, they might develop a condition known as “hemolytic anemia.” This means that red blood cells are destroyed and removed from the bloodstream sooner than they should be. 

When anemia happens, there are not enough red blood cells in the body to carry oxygen normally. This can cause a person to feel tired, be short of breath, and have a fast heartbeat. Also, when red blood cells are destroyed, a substance called bilirubin enters the bloodstream. High levels of bilirubin can lead to yellowing of the eyes and skin. The medical word for this is “jaundice.”

G6PD deficiency is one of the most common genetic enzyme deficiencies in the world. About 400 million people are affected. It is more common in males than females. It is also more common in people with African, Mediterranean, or Southeast Asian ancestry.

Some people may have a mild form of G6PD deficiency and others may have a more severe form. People with severe G6PD deficiency may have red blood cell destruction even if they are not exposed to any triggers. People with mild G6PD deficiency only have red blood cell destruction if it is triggered by a certain medicine or food.

G6PD deficiency is caused by inherited variations in the G6PD gene. Because this is a genetic condition, G6PD deficiency is a life-long condition.

Testing for G6PD deficiency

There are two ways to test for G6PD deficiency: a blood test for enzyme activity and a pharmacogenetic test. You may have had one or both of these tests done.

G6PD enzyme activity testing
A blood test can find G6PD deficiency. This test measures the activity of G6PD enzymes in the blood. People with low G6PD activity have G6PD deficiency.

G6PD pharmacogenetic testing
DNA is like a set of instructions for your body that can help decide how well your enzymes will work. Each person differs from another at the DNA (gene) level. This means each person has small differences in the genes that code for enzymes. The part of DNA that instructs how well G6PD enzymes will work is called the G6PD gene. The study of how genes like G6PD affect your response to medicines is called pharmacogenetics (FAR mah coh je NEH tiks).

Differences in your DNA that make up the G6PD gene can affect how well your red blood cells will react in certain times of stress. By testing your DNA (with a pharmacogenetic test), we may find differences that can allow us to predict how well your G6PD enzyme works. The results of this test will guide your doctor to avoid “trigger” medicines. The results of your G6PD pharmacogenetic test will place you into one of three groups:

Normal G6PD enzyme activity – People in this group have normal G6PD enzyme function. About 96 percent of people fall into this category.

G6PD deficiency – This means one or two copies of a gene have little or no G6PD enzyme function. People in this category should avoid taking certain medicines or eating certain foods to lower the risk of side effects like hemolytic anemia. About 2 percent of people fall into this category.   

Variable G6PD enzyme activity – This means one copy of a gene has little or no G6PD enzyme function and one copy of a gene has normal G6PD enzyme function. People in this category may need G6PD activity tests to find out if one gene is expressed more than the other. About 2 percent of people fall into this category. 

Medicines and foods to avoid with G6PD deficiency

Most of the time, people with G6PD deficiency can live healthy lives as long as they avoid certain foods and medicines that cause red blood cell damage. Examples of such foods and medicines include the following:

  • Foods to avoid:
    • Fava beans
  • Medicines to avoid:
    • Dapsone
    • Methylene blue
    • Nitrofurantoin
    • Pegloticase
    • Phenazopyridine
    • Primaquine
    • Rasburicase
    • Tafenoquine
  • Chemicals to avoid
    • Naphthalene (an ingredient found in moth balls)

A list of foods and medicines to avoid and medicines that should be used with caution in people with G6PD deficiency can be found at:  

Medical alert bracelet or card for G6PD deficiency

People with G6PD deficiency may benefit from having a medical alert bracelet or wallet pocket card that informs others of this condition. In an emergency, doctors can take this information into account before prescribing medicines.


If you have questions about which foods or medicines to avoid, contact your child’s doctor or pharmacist.

If you have questions or concerns about pharmacogenetic testing done at St. Jude, you can email the pharmacogenetics team at, or call one of the Pharmaceutical Sciences Research Nurses at 901-595-2482. If you are calling from outside of the Memphis area, dial toll free 1-866-2ST-JUDE (1-866-278-5833) and ask for extension 2482.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

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