A G6PD test measures the levels of glucose-6-phosphate dehydrogenase (G6PD), an enzyme (type of protein) in the blood.
G6PD helps red blood cells function normally. It also protects them from potentially harmful by-products that can accumulate when the body is fighting infection, or as the result of certain medications.
A G6PD test is a simple test that requires a blood sample. It is typically ordered to test for deficiencies of G6PD.
A G6PD deficiency is an inherited disorder that can lead to a certain type of anemia known as hemolytic anemia. Anemia is a blood disorder in which the body does not have enough red blood cells.
G6PD protects oxygen-rich red blood cells (RBCs) from chemicals called reactive oxygen, which build up in the body during a fever, infection, or when taking certain medications. If there is an insufficient amount of G6PD, RBCs will not be protected from these chemicals. The blood cells will die, leading to anemia.
In hemolytic anemia, the body is not able to produce enough RBCs to replace those that have been destroyed. Certain foods, medications, infections, and severe stress can trigger a hemolytic episode, which is the rapid destruction of RBCs.
Your doctor may order a G6PD test if he or she suspects hemolytic anemia based on certain symptoms, including:
- enlarged spleen
- pale skin
- rapid heart rate
- red or brown urine
- shortness of breath
A G6PD test is most often ordered when other causes of anemia and jaundice have been ruled out. The test will be performed once an episode has subsided.
The test may also be ordered to monitor treatments or to confirm the findings of other blood tests.
Blood draws are routine procedures that rarely cause any serious side effects.
In very rare cases, risks of giving a blood sample include:
- bleeding under the skin (hematoma)
- excessive bleeding
Tell your doctor what kinds of medication you are taking, from prescriptions to nutritional supplements. He or she may advise you to stop taking certain medications prior to the test, as they may alter the test results.
Inform your doctor if you’ve eaten any fava beans or taken “sulfa” drugs such as antibacterial drugs, diuretics (water pills), and anticonvulsants. All of these can produce adverse reactions, especially in people with G6PD deficiencies.
The test may be delayed if you are experiencing a hemolytic episode. According to the National Library of Medicine (NLM) many of the cells with low levels of G6PD are destroyed during an episode. As such, test results may show normal G6PD levels (NLM, 2012).
Your doctor will give you complete instructions on how to prepare for your blood draw.
The blood draw may be performed in a hospital or specialized testing facility.
Your skin will be cleaned before the test to prevent any microorganisms on your skin from contaminating the test. The nurse or technician will likely wrap a cuff or other pressure device on your arm. This will help the veins become more visible.
The technician will draw several samples of blood from your arm. He or she will place gauze and a bandage over the puncture site once the test is completed.
The blood samples will be sent to a laboratory for testing. Results will be forwarded to your doctor when they are complete.
When the results from your G6PD test are available, your doctor will discuss them with you at a follow-up appointment.
Low levels of G6PD in the blood indicate an inherited deficiency. There is no cure for this disorder. However, you can prevent hemolytic episodes and anemic symptoms by avoiding certain triggers. According to American Family Physician (AFP), triggers related to a G6PD deficiency include (AFP, 2005):
- fava beans
- aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen
- “sulfa” drugs, which are used to treat bacterial or fungal infections
- naphthalene, a compound found in moth repellent and toilet bowl deodorizers
Your doctor will discuss your results with you and will direct the next course of action.