This calculator helps determine your risk of having G6PD deficiency based on your ethnic background and gender. G6PD deficiency can cause severe hemolytic anemia when taking nitrofurantoin and other oxidizing drugs.
Your Risk Assessment
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Important Note: This calculator estimates your risk based on published prevalence data. It does not replace medical testing. If you're at high risk or have symptoms, consult a healthcare provider for G6PD testing.
Take a simple urinary tract infection (UTI). It’s common, treatable, and for most people, nitrofurantoin works fast and well. But for some, that same pill can trigger a life-threatening reaction - not because of an allergy, but because of a hidden genetic condition most never know they have: G6PD deficiency.
What Happens When Nitrofurantoin Meets G6PD Deficiency?
Nitrofurantoin is an old-school antibiotic, first used in the 1940s. It’s still prescribed today because it’s cheap, effective against common UTI bacteria like E. coli, and resistance rates are still low - around 10-15%. But here’s the catch: it’s also an oxidizing agent. In healthy people, red blood cells handle this just fine. Their natural defenses, powered by an enzyme called glucose-6-phosphate dehydrogenase (G6PD), keep oxidative stress in check.
In people with G6PD deficiency, that enzyme is broken or missing. Without it, red blood cells can’t repair damage from drugs like nitrofurantoin. The result? Hemoglobin clumps, cells burst, and hemolytic anemia kicks in. Symptoms show up fast - often within 24 to 72 hours: dark urine, extreme fatigue, jaundice, rapid heartbeat, and sometimes fever or confusion. In severe cases, hospitalization is needed. There have been documented deaths.
This isn’t theoretical. A 2022 review of medical literature found 42 confirmed or highly probable cases of nitrofurantoin-induced hemolytic anemia in G6PD-deficient patients. Ten of those were fatal. Eight cases involved pregnant women. Three involved infants - some exposed through breast milk or maternal use.
Who’s at Risk?
G6PD deficiency isn’t rare. It affects an estimated 400 million people worldwide. But it’s not evenly spread. If you’re of African, Mediterranean, Middle Eastern, or Southeast Asian descent, your risk is higher.
- Black African and African American populations: 10-14% carry the gene
- Mediterranean and Middle Eastern populations: 4-7%
- Southeast Asian populations: 2-5%
The CDC says nearly half of all people with G6PD deficiency don’t know they have it until they’re exposed to a trigger - like nitrofurantoin. That’s why screening matters.
Why Isn’t Everyone Tested Before Taking It?
The FDA label for nitrofurantoin clearly warns: “Hemolytic anemia has been reported in glucose-6-phosphate dehydrogenase (G6PD) deficient individuals.” But it doesn’t require testing before prescribing. Same with the European Medicines Agency - they updated their warning in 2021, but stopped short of making screening mandatory.
In real-world practice, that gap is deadly. A 2022 survey of 350 primary care doctors found only 32% routinely check G6PD status before prescribing nitrofurantoin. Why? Time, cost, assumptions.
G6PD testing costs $35-$50. A hospital stay for hemolytic anemia? $8,500-$12,000. Yet many doctors still skip the test, especially if the patient doesn’t “look like” they’re from a high-risk group. That’s dangerous thinking. G6PD deficiency doesn’t have a face. It doesn’t care if you were born in Birmingham, London, or Lagos. It only cares if your cells lack the enzyme.
What Do Experts Recommend?
The American Society of Hematology, the Clinical Pharmacogenetics Implementation Consortium (CPIC), and the CDC all agree: avoid nitrofurantoin in patients with known G6PD deficiency.
CPIC’s 2023 guidelines go further. They split recommendations into two groups:
- Patients with G6PD deficiency and no chronic hemolytic anemia: Use nitrofurantoin only if no alternatives exist - and monitor closely.
- Patients with G6PD deficiency and chronic hemolytic anemia: Absolutely avoid nitrofurantoin.
For most people, safer alternatives exist:
- Fosfomycin: Single-dose, no G6PD risk, good for uncomplicated UTIs
- Cephalexin: A first-generation cephalosporin, low risk of hemolysis
- Pivmecillinam: Used widely in Europe, low resistance, safe in G6PD deficiency
Trimethoprim-sulfamethoxazole (TMP-SMX) is common too, but it carries its own risks - including hemolysis in some G6PD-deficient patients. So it’s not automatically safer.
What If You’ve Already Taken It?
If you’re G6PD-deficient and took nitrofurantoin, stop immediately. Watch for signs:
Dark, tea-colored urine
Sudden fatigue or dizziness
Yellowing skin or eyes
Rapid heartbeat or shortness of breath
In most cases, symptoms resolve within 48-72 hours after stopping the drug, especially with fluids and rest. One 2023 case report described a patient whose hemoglobin dropped from 12.1 g/dL to 7.3 g/dL in three days - then rebounded to 11.5 g/dL after discontinuation, with no transfusion needed.
But don’t wait. If symptoms are severe - confusion, low blood pressure, or very low urine output - go to the ER. Hemolytic anemia can escalate quickly.
The Bigger Picture: Testing Is the Key
We’re moving toward personalized medicine. Point-of-care G6PD tests now exist - simple finger-prick devices that give results in 10 minutes. Some clinics in the U.S. and Europe are already using them in urgent care settings.
The NIH is running a trial (NCT04567891) to see if routine G6PD screening before nitrofurantoin use saves money and lives. Early data suggests it does. For every 1,000 high-risk patients screened, you prevent 15-20 hospitalizations.
Yet adoption is slow. Why? Because old habits die hard. Because testing isn’t built into most EHRs. Because many doctors still think, “It’s rare.” But if you’re one of the 1 in 10 Black men or 1 in 20 Mediterranean women with G6PD deficiency, “rare” doesn’t matter. It’s personal.
What Should You Do?
If you’re prescribed nitrofurantoin:
Ask: “Do I have G6PD deficiency?”
If you’re from a high-risk ethnic group, ask for a test before filling the script.
If you’ve had unexplained anemia, jaundice, or dark urine after antibiotics in the past, mention it.
If you’re pregnant or have a child with a UTI - ask if the antibiotic is safe for G6PD-deficient individuals.
If you’ve never been tested and you’re from a high-prevalence background, get tested. It’s quick. It’s cheap. It’s life-saving.
Nitrofurantoin isn’t evil. It’s a tool. And like any tool, it’s dangerous in the wrong hands - or the wrong body. Knowing your G6PD status doesn’t change your health. It just gives you control.
Can nitrofurantoin cause hemolytic anemia even if I don’t know I have G6PD deficiency?
Yes. About 50-60% of people with G6PD deficiency are undiagnosed until they take a drug like nitrofurantoin. The first sign of deficiency might be a sudden drop in hemoglobin, dark urine, or jaundice after starting the antibiotic. There’s no warning - it happens fast.
Is G6PD testing expensive or hard to get?
No. A standard G6PD blood test costs $35-$50 in the U.S. and is often covered by insurance. Many clinics offer rapid point-of-care tests that give results in under 10 minutes. You can get tested during a routine visit - no special appointment needed.
If I have G6PD deficiency, can I ever take nitrofurantoin again?
No. Once you’ve had a reaction, or even if you’re diagnosed with G6PD deficiency, you should avoid nitrofurantoin for life. Even small doses can trigger another episode. There are many other antibiotics for UTIs that are just as effective and completely safe.
Are there any other antibiotics I should avoid if I have G6PD deficiency?
Yes. Other oxidizing drugs include sulfonamides (like Bactrim), dapsone, primaquine, and methylene blue. Always check with your doctor or pharmacist before taking any new medication. Even some over-the-counter pain relievers like aspirin can pose a risk in high doses.
Can my children inherit G6PD deficiency if I have it?
Yes. G6PD deficiency is an X-linked genetic condition. If you’re male and have it, you’ll pass the gene to all your daughters (who become carriers) but not your sons. If you’re female and carry the gene, each son has a 50% chance of inheriting it, and each daughter has a 50% chance of being a carrier. Testing your children is recommended if you or your partner are from a high-risk population.
Why do some doctors still prescribe nitrofurantoin without testing?
Because guidelines aren’t always enforced. Many doctors rely on habit, not data. Nitrofurantoin is cheap, widely available, and works well - so it’s easy to default to. But when the cost of a $50 test prevents a $10,000 hospital stay, skipping it is a false economy. Awareness is growing, but change is slow.
Just got prescribed this for my UTI yesterday 😳 I’m Black American and had no idea about G6PD. I’m calling my doc first thing tomorrow to get tested. Thanks for posting this-could’ve been a nightmare.
Greg Robertson
January 19, 2026 AT 16:50 PM
My mom had a bad reaction to nitrofurantoin back in the 90s. They didn’t test her either. She ended up in the ER with jaundice and was so weak she couldn’t walk for weeks. Still sucks to think it was preventable.
Renee Stringer
January 20, 2026 AT 09:07 AM
It’s not just about testing-it’s about doctors taking responsibility. If you’re prescribing a drug with a known risk, you should be required to check. This isn’t ‘maybe’-it’s a documented danger. Stop being lazy.
Crystal August
January 20, 2026 AT 12:41 PM
Everyone’s acting like this is some new revelation. It’s been in the FDA label since the 80s. People just don’t read. Also, why are we acting like G6PD is some exotic condition? It’s common. Stop acting surprised.
