Blood test
G6PD Test
A G6PD test checks for a deficiency of an enzyme that protects red blood cells, which can make them break down with certain foods, medicines or infections.
Quick answer
G6PD Test: what it is and what the results mean
The G6PD test measures the activity of glucose-6-phosphate dehydrogenase, an enzyme that helps protect red blood cells from damage. A deficiency is an inherited condition that can lead to episodes of red cell breakdown (haemolysis).
- Why it is done: It is used to investigate unexplained anaemia or jaundice, especially after certain medicines, infections or eating fava (broad) beans, and to check for the condition before prescribing drugs that could trigger haemolysis.
- Understanding results: Low enzyme activity confirms G6PD deficiency.
What it is
The G6PD test measures the activity of glucose-6-phosphate dehydrogenase, an enzyme that helps protect red blood cells from damage. A deficiency is an inherited condition that can lead to episodes of red cell breakdown (haemolysis).
Why it is done
It is used to investigate unexplained anaemia or jaundice, especially after certain medicines, infections or eating fava (broad) beans, and to check for the condition before prescribing drugs that could trigger haemolysis.
What to expect
It is an ordinary blood test from a vein in the arm. Ideally it is done when you are not in the middle of a haemolytic episode, as levels can be misleadingly normal at that time.
Understanding the results
Low enzyme activity confirms G6PD deficiency. Knowing you have it allows you to avoid specific triggers such as certain medicines and fava beans, preventing episodes of red cell breakdown.
Good to know
Risks and limitations
It is a safe blood test, but a result taken during an acute episode can appear falsely normal because the most deficient cells have already broken down, so timing and sometimes repeat testing matter.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
G6PD Test: frequently asked questions
What should I avoid if I have G6PD deficiency?
You should avoid known triggers, which include fava (broad) beans and certain medicines. Your doctor will give you a list, and you should mention the condition before any new medicine is prescribed.
Why might the test be repeated?
During an episode of red cell breakdown, the most deficient cells are already gone, which can make the result look normal. Repeating the test later gives a more accurate measure.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- British Society for Haematology / relevant professional body
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