5-FU: What It Is, How It's Used, and What You Need to Know

When you hear 5-FU, a chemotherapy drug also known as fluorouracil, used to kill fast-growing cancer cells. Also known as fluorouracil, it's one of the most common chemotherapy agents used for colorectal, breast, and skin cancers. It doesn't just attack cancer—it affects any rapidly dividing cell in your body, which is why side effects like hair loss, mouth sores, and fatigue show up. But for many, it's a lifeline.

5-FU is often used alone or mixed with other drugs like leucovorin to boost its effect. It's given through an IV or applied as a cream for early-stage skin cancers like actinic keratosis. Doctors choose it because it’s been around for decades, works reliably, and fits into many treatment plans. It’s not a magic bullet, but for patients with certain tumors, it’s one of the most effective tools they have.

People using 5-FU need to watch for signs of low blood counts, which can lead to infections or bleeding. Some get severe diarrhea or hand-foot syndrome—red, painful, peeling skin on palms and soles. These aren’t rare. They’re expected. That’s why doctors run blood tests often and adjust doses. It’s not about avoiding side effects entirely—it’s about managing them so treatment can keep going.

There’s also a genetic angle. Some people have a variant in the DPYD gene that makes them extra sensitive to 5-FU. If you’re about to start treatment, asking for a simple blood test to check this could prevent a life-threatening reaction. It’s not standard everywhere, but it should be.

And while 5-FU is mostly used in hospitals or clinics, the cream version is something you can apply at home for precancerous spots. It burns. It stings. It makes your skin red and scaly. But for many, it stops skin cancer before it starts. No surgery. No scars. Just a daily application and patience.

The posts below cover real experiences and practical details about 5-FU and similar treatments. You’ll find comparisons with other chemo drugs, advice on handling side effects, and stories from people who’ve been through it. Whether you’re a patient, a caregiver, or just trying to understand what 5-FU really means in a treatment plan, this collection gives you the facts without the fluff.