Does this test have other names?
glucose-6-phosphate dehydrogenase deficiency test, G6PD deficiency test, G6PDD test
What is this test?
This is a blood test to find out if you have low amounts of an enzyme called glucose-6-phosphate
dehydrogenase. Experts estimate that 400 million people worldwide have a G6PD deficiency.
This enzyme deficiency is a genetic disorder that affects mostly males. A change (mutation)
in the G6PD gene causes the red blood cells to break down before they should. Early
blood cell destruction is called hemolysis. Some people who have the defective gene
never have any symptoms. Others have varying degrees of hemolytic anemia. This means
that red blood cells are destroyed faster than new ones can be made.
Most of the time, if you have a moderate deficiency of glucose-6-phosphate dehydrogenase,
you feel fine. But triggers can set off hemolysis. The effect is the sudden destruction
of older, more deficient red blood cells. These triggers include:
Why do I need this test?
You may need this test if you have some of these symptoms:
A newborn with G6PD deficiency can be born with jaundice. A baby might have this test
if symptoms such as dark urine, pale stools, and increasing bilirubin levels continue
after the second week of life.
What other tests might I have along with this test?
If you have only a mild to moderate deficiency and you have an important reason to
take a medicine that will trigger hemolysis, your healthcare provider may offer you
a low dose of the trigger medicine and keep track of your blood count closely. The
monitoring test is called a complete blood count.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
Here are some general results:
A normal test result tells your healthcare provider about G6PD activity in your blood
cells. A normal—or no G6PDD—result for adults is 8.6 to 18.6 units/gram of hemoglobin.
Less than 10% of normal means that you have severe deficiency and chronic hemolytic
Others with severe enzyme deficiency may not have chronic hemolytic anemia but will
have intermittent anemia.
Those with moderate deficiency, meaning 10% to 60% of normal ranges, may have intermittent
hemolytic anemia that is often linked to certain medicines or infection.
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
If you take this blood test during, or just after, a hemolysis episode, the result
could be falsely normal. The false-negative result could happen because most of the
blood cells with greater G6PD deficiency (the older ones) have already been destroyed
and the remaining blood cells are not, or not yet, G6PD-deficient. If your healthcare
provider believes you have a false-negative result, you will most likely have your
blood checked again in about 3 months. At this point, you'll have had time to develop
blood cells of various ages.
How do I get ready for this test?
You don't need to prepare for this test. Tell your healthcare provider about all medicines,
herbs, vitamins, and supplements you are taking. This includes medicines that don't
need a prescription and any illegal drugs you may use.