SGLT2 Inhibitors and Fournier’s Gangrene: Early Warning Signs and What to Do

When you’re managing type 2 diabetes, taking an SGLT2 inhibitor like canagliflozin, a sodium-glucose cotransporter-2 inhibitor that lowers blood sugar by making the kidneys flush out excess glucose through urine, can be life-changing. These drugs reduce heart failure risk, protect kidney function, and help with weight loss. But there’s a rare, serious side effect you need to know about - Fournier’s gangrene, a fast-spreading, life-threatening infection that destroys skin and tissue around the genitals and anus. It’s uncommon, but when it happens, every hour counts.

What Exactly Is Fournier’s Gangrene?

Fournier’s gangrene isn’t just a bad infection. It’s a necrotizing fasciitis - a type of bacterial invasion that eats through layers of tissue, starting in the genital or perineal area. The bacteria, often a mix of E. coli, Staphylococcus, and anaerobes, spread rapidly through the fascia, cutting off blood supply. Skin turns black, swelling becomes severe, and the pain? Patients describe it as worse than childbirth or a broken bone. Fever, chills, and a feeling of extreme sickness usually follow.

It’s not new. The condition was first described in 1764. But in the last decade, doctors started seeing it pop up in people taking SGLT2 inhibitors. Between 2013 and 2018, the U.S. FDA confirmed 12 cases linked to these drugs. By 2024, the number had climbed. Most cases were in men - but about one-third were in women. That’s important. Many still think this only affects men. It doesn’t.

Why Do SGLT2 Inhibitors Increase the Risk?

The answer lies in how these drugs work. Dapagliflozin, empagliflozin, and the others all force your kidneys to dump glucose into your urine. That sounds good - it lowers blood sugar. But it also means your underwear becomes a sweet, moist breeding ground for bacteria.

Think of it like leaving sugar water in a warm, dark place. Bacteria thrive. In some people, especially those with poorly controlled diabetes, the immune system can’t keep up. The glucose in urine weakens local defenses. The skin around the genitals gets irritated. A small cut, a yeast infection, or even friction from tight clothes can become an entry point. Once the bacteria get in, they multiply fast, and the infection spreads deeper than you’d expect.

It’s not just glucose. High blood sugar itself damages nerves and blood vessels. That means people with diabetes often don’t feel the early pain. They might ignore redness or swelling, thinking it’s just a rash. By the time they feel real pain, it’s already too late.

Early Warning Signs You Can’t Ignore

Here’s what to watch for - and don’t wait. If you’re on an SGLT2 inhibitor and notice any of these, go to the ER immediately:

• Severe pain in the genitals, anus, or inner thighs - worse than a urinary tract infection
• Swelling or redness that spreads quickly - not just a small area
• Dark or discolored skin - purplish, black, or bruised-looking patches
• Fever above 38°C (100.4°F) or chills
• Foul-smelling discharge from the genital area
• General feeling of being extremely ill - like you’re about to pass out

These symptoms don’t show up slowly. They can go from mild discomfort to life-threatening in under 24 hours. One patient in a 2022 study went from noticing redness to needing emergency surgery in 14 hours. Another waited two days because he thought it was a yeast infection. He didn’t survive.

What Happens If You Ignore It?

Delay kills. Studies show that for every hour treatment is delayed, the risk of death rises by about 9%. If surgery is delayed beyond 24 hours, mortality jumps from 4% to over 25%. That’s not a small risk. That’s a death sentence.

Doctors have to cut away dead tissue - sometimes entire sections of skin, muscle, and even parts of the penis or scrotum. They give strong antibiotics through IV. But if the infection has spread to the bloodstream, you could go into septic shock. Even with the best care, 4 to 8% of people with Fournier’s gangrene die. For those who survive, recovery takes months. Some need multiple surgeries. Others live with permanent changes to their body.

What to Do Right Away

If you suspect Fournier’s gangrene, here’s what you must do:

1. Stop taking your SGLT2 inhibitor immediately. Don’t wait for a doctor’s call. Don’t think it might be something else. Just stop.
2. Go to the nearest emergency room. Tell them you’re on an SGLT2 inhibitor and you have symptoms of possible Fournier’s gangrene. Say the words out loud - it helps them act fast.
3. Bring your medication bottle. The ER staff need to know exactly which drug you’re taking.
4. Do not delay. If you’re in pain, swollen, or feverish - don’t call your GP. Don’t wait until morning. Go now.

Emergency teams are trained for this. They’ll check your blood, do a CT scan, and if they see gas in the tissue - a sign of bacterial invasion - they’ll take you to surgery within hours. Time is everything.

Who’s at Highest Risk?

Not everyone on SGLT2 inhibitors will get this. The risk is still very low - about 2 in 100,000 people per year. But some people are more vulnerable:

• Those with HbA1c over 9% - poor blood sugar control
• People with a history of genital yeast or bacterial infections
• Those with weakened immune systems - from steroids, chemotherapy, or HIV
• People with obesity or poor hygiene in the genital area
• Men over 50 - though women are at risk too

If you fit even one of these, talk to your doctor. You might still be a good candidate for the drug - but you need to be extra careful.

The Bigger Picture: Benefits vs. Risk

Let’s be clear: SGLT2 inhibitors save lives. They cut heart failure hospitalizations by up to 30%. They slow kidney disease in people with diabetes. For many, they’re the difference between needing dialysis and staying active into their 70s.

The FDA, the European Medicines Agency, and Australia’s TGA all still recommend these drugs - but with a warning. The benefits outweigh the risk for most people. But that doesn’t mean you can ignore the signs.

Doctors now train patients like this: "If you’re on this drug, treat any genital pain or swelling like you would a heart attack. Act fast. Don’t wait. Call 911. Go to the ER."

What Your Doctor Should Tell You

At your next appointment, ask: "Do I need to know about Fournier’s gangrene?" If they don’t bring it up, they’re not giving you full information. You deserve to know the risks.

Good doctors now use clear language: "This drug makes your urine sugary. That can lead to a rare but deadly infection. If you get pain, swelling, or fever in your groin, go to the ER right away. Don’t wait. Don’t call me. Go."

It’s not about scaring you. It’s about giving you power. You can keep the benefits of the drug - and avoid the worst outcome - if you know what to look for.

What Happens After You Recover?

If you survive Fournier’s gangrene, you’ll likely need to stop SGLT2 inhibitors for good. Your doctor will switch you to another class of diabetes medication - maybe a GLP-1 agonist like semaglutide, or insulin. You’ll also need to manage your blood sugar tighter than ever. And you’ll need to check your genital area daily for any changes.

Some patients need reconstructive surgery. Others deal with chronic pain or nerve damage. Recovery isn’t just physical - it’s emotional too. But knowing what to watch for next time? That’s how you protect yourself.