G6PD Deficiency Risk Calculator
This tool helps you understand your personal risk of G6PD deficiency based on your ancestry and symptoms. G6PD deficiency can cause severe anemia when taking nitrofurantoin, a common urinary tract infection antibiotic.
Select your ancestral background:
Have you experienced any of these symptoms after taking medications?
Recommended Actions
Every year, millions of people take nitrofurantoin to treat a simple urinary tract infection. It works fast, it’s cheap, and for most people, it’s safe. But for a significant number of others, this common antibiotic can trigger a life-threatening reaction they never saw coming. The problem isn’t the infection-it’s what happens inside their body when nitrofurantoin meets a hidden genetic condition called G6PD deficiency.
What Is G6PD Deficiency?
G6PD deficiency is a genetic condition that affects how your red blood cells handle stress. It’s caused by a lack of an enzyme called glucose-6-phosphate dehydrogenase, which normally protects red blood cells from damage caused by oxidative chemicals. Without enough of this enzyme, your red blood cells become fragile and can burst open when exposed to certain triggers-like some medications, infections, or even fava beans.
This isn’t rare. Around 400 million people worldwide have it, according to the World Health Organization. It’s most common in people of African, Mediterranean, Middle Eastern, and Southeast Asian descent. In Black populations, up to 1 in 10 men have it. Many people live their whole lives without knowing they have it-until they take a drug like nitrofurantoin.
How Nitrofurantoin Triggers Hemolytic Anemia
Nitrofurantoin kills bacteria by creating reactive chemicals in the urine. That’s great for fighting UTIs. But in people with G6PD deficiency, those same chemicals leak into the bloodstream and attack red blood cells. The cells can’t defend themselves. They break apart. That’s hemolytic anemia-when your body destroys red blood cells faster than it can replace them.
The signs come fast. Within 24 to 72 hours of taking the first dose, you might feel feverish, dizzy, or unusually tired. Your skin or eyes could turn yellow. Your urine may look dark-like tea or cola. Blood tests show dropping hemoglobin, rising bilirubin, and low haptoglobin. In severe cases, kidney damage or shock can follow.
Studies have tracked over 300 cases of nitrofurantoin-induced hemolytic anemia. Of those, 42 were confirmed in G6PD-deficient patients. Ten ended in death. Most of those who survived recovered quickly once the drug was stopped-but only because they got care in time.
Who’s at Risk?
If you’re from a population with high G6PD deficiency rates, you’re at risk-even if you’ve never had symptoms before. That includes:
- Men of African or African American descent
- People with ancestry from the Mediterranean (Greece, Italy, Turkey)
- Those from the Middle East (Saudi Arabia, Iraq, Iran)
- Individuals from Southeast Asia (Thailand, Cambodia, Philippines)
Women can carry the gene too, though symptoms are often milder. Pregnant women with G6PD deficiency are especially vulnerable-nitrofurantoin can cross the placenta and harm the baby. Infants exposed through breast milk or in utero have also developed hemolytic anemia.
And here’s the scary part: most doctors don’t test for it before prescribing nitrofurantoin. A 2022 survey of 350 primary care doctors found only 32% routinely check G6PD status before giving this drug. Even though major groups like the American Society of Hematology and the Clinical Pharmacogenetics Implementation Consortium (CPIC) say you should avoid it entirely if you have G6PD deficiency.
What Does the Evidence Say?
The data is clear. Nitrofurantoin is one of the top drugs linked to oxidative hemolytic anemia-not because it’s toxic to everyone, but because it’s deadly to people with this specific genetic flaw.
The CPIC, which sets global standards for drug-gene interactions, says nitrofurantoin should be avoided completely in G6PD-deficient patients who’ve had chronic hemolytic anemia. For others with G6PD deficiency, it’s a strong caution-use only if no other option exists.
Compare it to alternatives. Trimethoprim-sulfamethoxazole (TMP-SMX) has slightly higher resistance rates in E. coli, but it doesn’t cause this kind of reaction. Fosfomycin is another safe option for UTIs in G6PD-deficient patients. Both are recommended by guidelines as first-line alternatives.
Even the FDA’s own label for nitrofurantoin warns about hemolytic anemia in G6PD-deficient individuals. But it doesn’t require testing. That’s a gap between what’s known and what’s done.
Why Isn’t Everyone Tested?
The cost of a G6PD test is around $35 to $50. A hospital stay for hemolytic anemia? That’s $8,500 to $12,000. So why don’t we just test everyone at risk?
Partly because testing isn’t automatic. Most clinics don’t have point-of-care tests. Blood draws take time. Results can take days. In a busy office, it’s easier to prescribe the drug and hope for the best.
Also, many patients don’t know their heritage puts them at risk. If you’re a first-generation American, or your family never talked about medical history, you might not even know you’re from a high-risk group.
And here’s the twist: half to 60% of people with G6PD deficiency don’t know they have it until they have a reaction. That’s not ignorance-it’s a system failure.
What Should You Do?
If you’ve been prescribed nitrofurantoin for a UTI, ask yourself these questions:
- Do I or my ancestors come from Africa, the Mediterranean, the Middle East, or Southeast Asia?
- Have I ever had unexplained jaundice, dark urine, or extreme fatigue after taking a medication?
- Have I ever had a family member with anemia or jaundice?
If the answer is yes to any of these, ask your doctor: “Could I have G6PD deficiency? Can we test for it before I start this drug?”
If you’re already taking nitrofurantoin and feel worse after a day or two-fever, chills, yellowing skin, dark urine-stop the drug and get medical help immediately. Don’t wait. Hemolytic anemia can escalate fast.
What Are the Alternatives?
You don’t need nitrofurantoin to treat a simple UTI. Here are safer options for people with G6PD deficiency:
- Fosfomycin (Monurol): A single-dose antibiotic, highly effective, no known hemolytic risk.
- Cephalexin or other cephalosporins: Generally safe, though they can cause immune hemolytic anemia in rare cases (different mechanism).
- Pivmecillinam: Used in Europe, low resistance, safe in G6PD deficiency.
- Amoxicillin-clavulanate: Often used as second-line, safe in most G6PD cases.
These alternatives aren’t always first choice because they’re more expensive or less familiar to some doctors. But they’re safer-and that matters more than cost or habit.
What’s Changing?
Change is coming, slowly. The global market for G6PD testing is expected to grow from $185 million in 2022 to over $310 million by 2027. Point-of-care tests are being developed-some can give results in 15 minutes during a clinic visit.
The NIH is running a trial to see if universal G6PD screening before nitrofurantoin use saves money and lives. Early results are expected soon.
Electronic health records are starting to add alerts. If your profile shows African or Mediterranean ancestry, your doctor’s system might now pop up a warning: “G6PD deficiency risk. Consider alternative for UTI.”
But until those systems are universal, the burden is on you. If you’re at risk, speak up. Ask for the test. Push for safer options. Your life might depend on it.
Final Thoughts
Nitrofurantoin isn’t evil. It’s a useful tool. But like any tool, it’s dangerous in the wrong hands-or the wrong body. G6PD deficiency isn’t a flaw. It’s a biological variation. And we’ve failed to treat it like one.
For millions, nitrofurantoin is a lifesaver. For others, it’s a silent threat. The difference isn’t luck. It’s knowledge. And knowledge should be part of every prescription.
7 Comments
Nitrofurantoin is a perfect example of how medicine still treats genetic diversity like a glitch instead of a variable. We test for everything else-drug interactions, liver enzymes, allergies-but we just hand out this drug like it’s candy to people whose ancestors survived malaria for centuries? That’s not medicine, that’s colonialism with a stethoscope.
Just got prescribed this last week. My grandma was from Jamaica. I’m gonna call my doctor tomorrow and ask for the test. Don’t wanna end up in the ER because some doc thought ‘African descent’ meant ‘I’m tough.’
Good post. Real talk: if you’re from a high-risk group and your doctor doesn’t offer a G6PD test before nitrofurantoin, ask for it. It’s a simple finger prick. If they say no, get a second opinion. Your blood cells aren’t disposable.
Oh great, now we’re testing people for their ancestry before giving them antibiotics? Next they’ll ask if you’re related to someone who had a spleen removed in 1973. This is why healthcare is a joke.
Let’s be real-most people who get hemolytic anemia from nitrofurantoin are already symptomatic. The real issue isn’t the lack of testing, it’s that people ignore symptoms until they’re in shock. If you’re tired, jaundiced, and your pee looks like root beer, stop taking the drug. Not because of genetics-because you’re clearly not well.
As a nurse, I’ve seen this happen too many times. A patient comes in with dark urine after a UTI script, and we find out they’re G6PD deficient. Their doctor didn’t ask about ancestry. They didn’t even know their mom had jaundice as a baby. This isn’t about blame-it’s about systems failing people who don’t even know they’re at risk. We need better protocols.
My cousin in Delhi got this drug for a UTI and turned yellow in 36 hours. No one knew he had G6PD deficiency. They thought it was ‘liver trouble.’ He spent a week in ICU. Now my whole family got tested. If you’re from South Asia, don’t wait for the emergency room to teach you. Get tested. It’s 35 bucks and it could save your life.