Medical Oncologist
CION Cancer Clinics
G6PD deficiency and the medicines used in cancer care | CION Cancer Clinics
G6PD deficiency is an inherited enzyme condition that leaves red blood cells easily damaged by certain medicines. It does not stop cancer treatment. It changes which supporting medicines are safe, most importantly rasburicase, a drug used to lower uric acid in leukaemia and lymphoma. This page explains who is affected, how the blood test works, which medicines matter and the warning signs to act on the same day. At CION Cancer Clinics, our team helps carriers and their families plan checks, next steps and support after a genetic result.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- Why does G6PD deficiency matter during cancer treatment?
- Which medicines around cancer treatment need a G6PD check?
- How is G6PD deficiency tested?
- The words you will meet, in plain language
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about G6PD deficiency and cancer medicines
The short answer
Why does G6PD deficiency matter during cancer treatment?
G6PD deficiency is an inherited condition in which red blood cells lack an enzyme that protects them from damage. Most people with it feel completely well. The problem comes when certain medicines are given, because in a person with low G6PD those medicines can make red cells break apart quickly.
How common is it in India?
It is one of the most common inherited enzyme conditions in the world, and it is found across India. It is more frequent in some communities than others, and marriage within a community can keep it concentrated in a family. Many adults who have it were never tested and have no idea.
Why cancer care brings it to light
A few medicines used alongside cancer treatment are among the recognised triggers. The best known is rasburicase, a drug used to bring down very high uric acid when a fast-growing leukaemia or lymphoma starts to break down. That is why a G6PD check may appear on your blood form before such treatment begins.
G6PD deficiency does not cause cancer and does not make cancer treatment impossible. It changes which supporting medicines are safe.The medicines that matter
Which medicines around cancer treatment need a G6PD check?
These are the ones oncology teams think about most. The list is not complete, so always show your result to anyone prescribing for you.
Rasburicase
Given to lower uric acid quickly when a large tumour breaks down at the start of treatment. In G6PD deficiency it is not safe to use. Other uric acid medicines, such as allopurinol, are chosen instead.
Dapsone
Sometimes used to prevent a serious lung infection in people whose immunity is low after treatment. It can trigger red cell breakdown, so the team will check your G6PD first and may pick another option.
Methylene blue
Used for a few rare treatment complications, including confusion caused by the chemotherapy drug ifosfamide. In G6PD deficiency it can do harm rather than help.
Outside the cancer ward
Triggers you may meet at home or in another clinic.
- Primaquine and some other malaria tablets
- Nitrofurantoin for urine infections
- High-dose vitamin C drips
- Fava beans, also called broad beans
Not sure whether this applies to you?
Ask an oncologistHow it is checked
How is G6PD deficiency tested?
A simple blood sample
The usual test measures how much working enzyme your red cells contain. No fasting is needed. It is often added to the routine bloods taken before treatment starts.
A screening result or a measured level
Some labs give a quick normal or deficient answer. Others report an actual activity level, which is more useful for women and for results that sit near the borderline.
Timing can mislead
Straight after a blood transfusion, or after a recent episode of red cell breakdown, the level can look falsely normal. Your doctor may repeat the test later.
A gene test is occasionally added
Reading the G6PD gene itself is useful when the enzyme result is unclear, or when a family wants to know who carries it. For most treatment decisions the enzyme test is enough.
On your report
The words you will meet, in plain language
- G6PD
- Short for glucose-6-phosphate dehydrogenase, the enzyme that shields red blood cells from chemical damage.
- Deficient
- Enzyme activity is low enough that trigger medicines should be avoided.
- Intermediate
- Activity is partly reduced. This is common in women who carry the condition, and the safe choice of medicine depends on the drug.
- Haemolysis
- Red blood cells breaking apart faster than the body can replace them. It causes the warning signs described below.
- X-linked
- The gene sits on the X chromosome. Men have one X, so one faulty copy is enough to affect them. Women have two, so they are more often carriers.
- Carrier
- Someone with one faulty copy who may have normal or partly reduced activity, and who can pass it to a child.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
!
Signs that cannot wait
If you have G6PD deficiency, or have not been tested, and within a day or two of a new medicine your urine turns dark like tea or cola, your eyes or skin turn yellow, or you become suddenly breathless and pale, go to the nearest emergency department the same day. Take the medicine strip with you and say that G6PD deficiency is possible. Do not take another dose while you wait to be seen.
Being straight with you
What this page cannot tell you
It cannot tell you whether a particular medicine is safe at your particular enzyme level. Some drugs are risky at any level of deficiency. Others are acceptable with close monitoring. That judgement belongs to the doctor prescribing, with your result in front of them.
It cannot explain a borderline result
Results near the cut-off, results in women, and results taken soon after a transfusion are the ones most often misread. What your specific result means is a question for the doctor who ordered the test, or for a haematologist.
Who this does not apply to
Most people do not have G6PD deficiency, and a normal result closes the question for good because it is inherited and does not change. If your treatment plan contains none of the trigger medicines, the result will not alter it. This page is also not about the tumour tests that guide targeted drugs, which look at the cancer rather than at you.
Brothers, sons and maternal relatives of a man with G6PD deficiency may also have it. A simple blood test tells them.Commonly believed
Four things families tell us, and what is actually true
"I have never been ill from it, so it does not matter."
Most people with G6PD deficiency feel well until they meet a trigger. Having no problems so far usually means the trigger has not happened yet, not that the condition is harmless.
"Only men can have it."
Men are affected more often, but women can have reduced enzyme activity too. A woman's result can also look normal on a quick screening test while her activity is actually lower than it seems.
"With G6PD deficiency I cannot have chemotherapy."
The main chemotherapy drugs are not the usual problem. The concern is a small group of supporting medicines, and each of them has an alternative your team can use.
"Vitamin C drips are natural, so they are safe."
High-dose vitamin C given into a vein is a known trigger for red cell breakdown in G6PD deficiency. Tell your oncologist before accepting any drip from another clinic.
Questions we are asked
Common questions about G6PD deficiency and cancer medicines
Why was G6PD added to my blood tests before treatment?
Usually because your plan may need a medicine such as rasburicase, which is not safe in G6PD deficiency. Checking first lets the team choose the right option without delay. It is a routine safety step, and it does not mean anyone suspects a problem.
What happens if rasburicase is needed urgently?
The G6PD test can often be done quickly. If the result is not available in time and your risk is uncertain, the team can use a different uric acid medicine, plenty of fluids and close blood monitoring until the result comes back.
Is G6PD deficiency the same as a low haemoglobin?
No. G6PD deficiency is an enzyme problem you are born with. Your haemoglobin is usually normal. It only drops suddenly if red cells break down after a trigger. A low haemoglobin during chemotherapy usually has other causes.
My child had a G6PD result at birth. Is that still valid?
Usually yes, because the condition does not change. Bring the old report, or the newborn screening card, to your oncologist. If the result was borderline or the paperwork is unclear, the test is simple to repeat.
Should my family be tested?
It is worth considering, especially for brothers, sons and relatives on the mother's side. Knowing in advance protects them if they are ever prescribed a trigger medicine. It is a blood test, and no genetic counselling is usually needed for it.
Can antibiotics during chemotherapy cause a problem?
Most antibiotics used during cancer treatment are fine. A few, including nitrofurantoin and some sulfa-type antibiotics, carry a risk. Tell every doctor about your G6PD result, including those who treat an infection outside the cancer centre.
Do I need to change my diet?
Avoid fava beans, also sold as broad beans. Ordinary Indian dals and other pulses are not the concern. Some herbal and home remedies have been linked to red cell breakdown, so check any remedy with your oncologist before taking it.
Does a G6PD result affect a bone marrow transplant?
It can affect which supporting medicines are used, including some that prevent infections while immunity is low. The condition itself does not rule out a transplant. Your transplant team will plan the supporting medicines around your result.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- MedlinePlus Genetics — Glucose-6-phosphate dehydrogenase deficiency
- MedlinePlus — G6PD Test
- U.S. Food and Drug Administration — Table of Pharmacogenomic Biomarkers in Drug Labeling
- Clinical Pharmacogenetics Implementation Consortium (CPIC) — Guidelines
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Which cancer drugs have a gene test firstThe other medicines where a check comes before the first doseHLA testing before certain medicinesA different inherited check, for severe skin reactionsCarrying your drug-gene result forwardMake sure every future prescriber sees your resultWhy your genes change your doseThe idea behind all drug-gene testing, simply explained
Talk to us
Have a G6PD result and a treatment plan to check?
Bring your G6PD report and your list of medicines. An oncologist will check the plan against the result with you. One helpline serves every CION centre.