The G6PD gene helps red blood cells defend themselves against everyday chemical stress. This gene helps your body keep those cells stable; if it does not work well, certain medicines, infections, or fava beans can trigger red blood cells to break down, leading to anemia, jaundice, dark urine, and tiredness. Many people with a G6PD variant stay well most of the time and only notice problems after a trigger. G6PD is widely known through “favism,” the reaction some people have after eating fava beans.
What is a gene?
Genes are stretches of DNA that hold instructions your cells use to make molecules or regulate activities in the body. Some genes carry the directions for producing proteins, which are the working parts of cells. Others mainly guide when certain processes take place, where they occur, and how strongly they run. Together, genes affect how the body develops and functions, and they can also shape how you respond to food, stress, or medications. For a deeper look at this topic, you can learn more in the LearnHub.
Overview
G6PDGene function
What if the gene works
The G6PD gene helps cells make a protein that protects them from everyday chemical stress. This protection is especially important in red blood cells, which need it to stay healthy and carry oxygen.
Risk
What if the gene does not work
Variants in the G6PD gene can make red blood cells break down, often during infections or after certain medicines or fava beans. This may cause jaundice or anemia. Milder and more severe variants can change symptom timing and severity.
Treatment
What does that mean for your treatment
A pathogenic or loss-of-function variant in the G6PD gene can change drug choices because medicines that increase oxidative stress may trigger hemolysis. Clinicians usually avoid rasburicase, and primaquine or tafenoquine may be used only with great caution; other oxidant drugs may also be avoided. If hemolysis occurs, treatment centers on stopping the trigger and giving supportive care, sometimes including transfusion.
Conditions associated with G6PD
Gene function
What if the gene works
Your red blood cells and many other cells use the G6PD gene to make an enzyme that helps them handle normal daily wear. It supports a healthy chemical balance inside cells and helps supply certain basic parts needed for growth and renewal. This steady work is especially important in cells that face a lot of oxygen, such as red blood cells.
The G6PD gene helps cells make NADPH, a small helper molecule that powers antioxidant defenses. This lets cells neutralize unstable substances formed during normal metabolism and daily exposures.
Red blood cells rely on the G6PD gene to keep hemoglobin and the cell membrane in good working order. This is central to how the G6PD gene helps protect red blood cells while they carry oxygen through the bloodstream.
The enzyme made from the G6PD gene begins a cell process that also produces ribose-5-phosphate, a sugar used to build DNA and RNA. This supports normal cell growth, renewal, and repair.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These changes are common and help shape normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not cause any noticeable effects and simply represent natural genetic variation. In some situations, though, a variant can change how a gene works more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the G6PD gene can alter the enzyme's shape or stability, so red blood cells have less working protein. This is how G6PD gene variants affect enzyme activity and lower NADPH, a molecule that helps protect cells from chemical stress. Milder variants often leave partial activity, while more severe variants may leave very little, which can make red blood cells break apart more easily and can lead to earlier or more frequent symptoms in G6PD deficiency.
How variants are linked to conditions
Pathogenic variants in the G6PD gene cause G6PD deficiency, a condition linked to episodes of hemolytic anemia and newborn jaundice. G6PD deficiency symptoms may appear after certain medicines, infections, or fava beans, while some people have few or no day to day problems. The condition varies by the specific variant and is often more noticeable in males, though females can also be affected.
A variant is not necessarily a diagnosis
Genetic variants are common across the general population and are a normal feature of human biology. Most do not directly affect health and simply contribute to natural differences among people. For many genes, having a variant associated with a condition points to a possible link rather than a definite diagnosis, particularly when several genes and environmental influences play a role. In some situations, though, one well-characterized variant in a particular gene is enough to confirm the diagnosis.
Are there things that can increase or change my risk?
For people with a G6PD change, the main thing that changes risk is exposure to triggers rather than lifestyle alone. Hemolytic episodes, where red blood cells break down too quickly, are more likely with certain medicines, fava beans, and some infections, and risk can also vary by the specific gene change and by sex.
Inheritance of G6PD variants
Variants in the G6PD gene are inherited in an X linked pattern, which is the usual G6PD inheritance pattern seen in families. Because the gene is on the X chromosome, fathers pass their X chromosome to all daughters and none of their sons, while mothers can pass the variant to children of either sex. Sons who inherit a disease causing variant are more likely to have symptoms because they have one X chromosome. Daughters may be carriers, and some may also have symptoms, especially if they inherit a variant from both parents or have uneven X chromosome activity.
What does my G6PD result mean for my family?
G6PD-related conditions usually run in families in an X-linked pattern, so close relatives on the mother’s side may also carry the gene change or have symptoms. Male relatives are more likely to have clear symptoms, while female relatives may be carriers and can sometimes have milder symptoms too. Brothers, sisters, and children may also be affected depending on which parent carries the change.
Genetic information
Genetic testing
How you find out about variants
Variants in the G6PD gene are found with G6PD genetic testing, usually from a blood sample, cheek swab, or saliva sample. A lab reads the DNA code in the G6PD gene and checks for known variants. Results can confirm an inherited cause of low G6PD activity and help clarify family risk.
When should I consider getting a genetic test?
Genetic testing for the G6PD gene can be worth considering if there is a family history of G6PD deficiency, episodes of yellowing of the skin, dark urine, or sudden anemia after certain medicines, infections, or fava beans. It may also help explain severe newborn jaundice.
A genetic result is only one part of your health story
A genetic result can provide valuable insight, but how much it explains varies by the condition and the kind of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body functions over time. In some conditions, especially those shaped by many genes, genetic information gives context rather than certainty and is most useful when considered together with other parts of care. In other situations, a genetic result may offer a clear answer. In areas such as medication response, genetic results can help put personal experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Variants in the G6PD gene can make certain medicines, especially rasburicase, more likely to trigger red blood cell breakdown (hemolysis). This happens because the body’s red blood cells may have less protection against chemical stress from some drugs. Genetic differences like this are common and help explain why the same medicine may be tolerated well by one person but cause side effects or work differently in another.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes can affect the way they respond to medicines. It studies gene and drug patterns to help explain why the same treatment may work differently in different people. For many medications, genes can influence how strongly a drug works or how the body handles it. This information can support treatment choices that are more informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the G6PD gene
When should I seek medical advice?
If you know you have a change in the G6PD gene, or G6PD deficiency runs in your family, talk with your doctor before starting certain medicines, especially some malaria treatments and rasburicase. This matters because these drugs can trigger sudden breakdown of red blood cells in people with G6PD deficiency. Seek prompt medical care for dark urine, yellowing of the eyes, unusual tiredness, shortness of breath, or pale skin after a new medicine.
History
Throughout history, people described episodes of jaundice and dark urine after fava beans or certain medicines, long before the cause was known. In the mid 20th century, researchers linked these reactions to a missing or reduced activity of the G6PD gene, especially after some people developed hemolytic anemia while taking the antimalarial drug primaquine. Initially understood only through visible traits, later recognized as tied to a specific gene, this finding became a landmark in both blood medicine and pharmacogenetics. Studies also showed that the condition was more common in parts of Africa, the Mediterranean, the Middle East, and Asia, shaping ideas about inherited protection against severe malaria. With each decade, genetic studies refined the picture, revealing many different G6PD variants across populations.