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Diarrhea

Diarrhea is common with drugs like irinotecan, 5-FU, Verzenio and others. With immunotherapy, it can be a sign of colon inflammation and needs a call to your team.

When it happens

Timing depends on the drug.

What helps at home

Drink 8–12 cups of clear fluid a day unless told otherwise.
Eat small meals of low-fiber foods like bananas, white rice, applesauce and toast.
Limit greasy, spicy, high-fiber foods, alcohol and caffeine.
Only take anti-diarrhea medicine your team approves.
Use gentle wipes and barrier cream.

Call your care team now if you have:

Many loose stools in a day, or diarrhea lasting more than a day (ask your team what number should prompt a call)
Blood in your stool or black stool
Fever, dizziness or peeing much less
Any diarrhea while on immunotherapy (Keytruda, Opdivo)

Call 911 for trouble breathing, chest pain or signs of stroke.

Drugs on this site linked to diarrhea

💬 What experts are saying

Breast cancer specialists on OncLive say low white blood cells is the main thing they watch for with drugs like Ibrance. With Verzenio, diarrhea is the main concern: they advise keeping an anti-diarrhea medicine at home, starting it at the first loose stool, and eating blander, lower-fiber meals. They also note it often settles down after the first several weeks.

Source: HR+/HER2- MBC: CDK4/6 Inhibitor Treatment Toxicities (OncLive, November 1, 2021)

Find support

CancerCare: Free counseling, support groups and financial help
Cancer Support Community: Support groups, a helpline and the MyLifeLine online community
Imerman Angels: Free one-on-one matching with a survivor or caregiver mentor
American Cancer Society: 24/7 helpline (1-800-227-2345), rides to treatment, lodging and information

Common questions

How long does chemo diarrhea last?

It depends on the drug. Call if it lasts more than a day or is severe.

Written by the Cancer Side Effects Guide team from FDA labels and leading cancer centers. Not medical advice. · Last updated: October 15, 2026 · How we write

Not medical advice. This page is general information to help you talk with your care team. It can't replace advice from your doctor or nurse. If you have a fever of 100.4°F (38°C) or higher during treatment, or any symptom that worries you, call your care team now. In an emergency, call 911.