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G6PD and G6PD Deficiency

What is G6PD?

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

Hemolytic anemia

People with G6PD deficiency are at a higher risk for red blood cell destruction. This is especially true after they are exposed to triggers such as 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 blood sooner than they should be. 

In anemia, there are not enough red blood cells in the body to carry oxygen normally. This can cause a person to feel tired, short of breath, and have a fast heartbeat. Also, when red blood cells are destroyed, a substance called bilirubin enters the blood. High levels of bilirubin can lead to yellowing of the eyes and skin, or jaundice.  

Causes of G6PD deficiency

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

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

Testing for G6PD deficiency

There are two ways to test for G6PD deficiency: a blood test for enzyme activity and a pharmacogenomic test. You may have one or both tests performed.

G6PD enzyme activity testing

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

G6PD pharmacogenomic testing

Each person differs from another at the DNA level. Genes are segments of DNA that act as a set of instructions and tell the body how to work. The G6PD gene is a section of DNA that instructs how well G6PD enzymes will work. 

The study of how genes like G6PD affect the way your body interacts with medicines is called pharmacogenomics. Differences in your DNA that make up the G6PD gene can change how your red blood cells react with some medicines. A pharmacogenomic test looks for these differences.

A pharmacogenomic test looks for differences that can help your medical team know how well your G6PD enzymes will work. The test results can help you know if you need to avoid certain foods and medicines.  

Find more information about genes that are being used to make drug therapy decisions for patients at St. Jude.   

If you have questions about pharmacogenomic testing done at St. Jude, you can email the Clinical Pharmacogenomics Program at

G6PD gene groups

The results of your G6PD test will place you into one of three groups:

Normal G6PD enzyme activity – People in this group have normal G6PD enzyme function.  

G6PD deficiency – This means there is 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.  

Variable G6PD enzyme activity – This means you may have normal G6PD enzyme activity or a G6PD deficiency.  The group you are in could change throughout your life. People in this category may need G6PD activity testing to know how well their G6PD enzymes work.  

Risk of G6PD deficiency  

For females, about 95% of people are in the normal activity group, 4% are in the variable activity group, and 1% are in the deficient group.

For males, 97% of people are in the normal activity group and 3% are in the variable group. 

Medicines and foods to avoid with G6PD deficiency

Most of the time, people with G6PD deficiency can live healthy lives. But they need to avoid certain foods and medicines that cause red blood cell damage.  

Medicines to avoid:

  • Dapsone
  • Methylene blue
  • Pegloticase
  • Primaquine at standard doses >0.25-0.5 mg/kg/day for 14 days)
  • Rasburicase
  • Tafenoquine
  • Toluidine blue

Foods to avoid:

  • Fava beans

Chemicals to avoid:

  • Naphthalene (an ingredient found in moth balls)

Medicines and foods to use with caution with G6PD deficiency:

  • Nitrofurantoin
  • Primaquine at medium doses (0.75 mg/kg or 45 mg once weekly for 8 weeks)

A more detailed list of medicines to avoid or use 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 use this information to help make decisions about medicines.

Key Points

  • G6PD is an enzyme that helps protect red blood cells.  
  • People with G6PD deficiency can have red blood cell destruction if they have certain medicines or foods.
  • Testing can help identify people with G6PD deficiency. This helps doctors and pharmacists know which medicines should be used with caution or avoided.

Reviewed: August 2022