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GLP-1 diarrhea: how common it is, how long it lasts, what helps

Updated Sep 27, 2026. Numbers in brackets link to the source each fact comes from.

Diarrhea is one of the most common side effects of GLP-1 medicines, but a large share of it shows up on placebo too. On the Wegovy injection, for example, 30% of people in the weight trials reported diarrhea, and so did 16% of people taking a dummy shot [5]. It was most common while the dose was being raised, and the labels say it became less frequent afterward.

How often it happened in the trials

The table shows the share of trial participants with diarrhea on each medicine and on placebo. The Zepbound row counts both diarrhea and frequent bowel movements [3]. The column order for each drug comes from the table header on its label.

Medicine and trial group Placebo On the medicine
Zepbound 5, 10 and 15 mg, weight trials 8% 19%, 21%, 23% [1] [2]
Wegovy injection 2.4 mg, weight trials 16% 30% [4] [5]
Foundayo 5.5, 9 and 17.2 mg, weight trials 11% 21%, 23%, 25% [7] [8]
Ozempic 0.5 and 1 mg, diabetes trials 1.9% 8.5%, 8.8% [9] [10]
Mounjaro 5, 10 and 15 mg, diabetes trials 9% 12%, 13%, 17% [11] [12]

The Wegovy label has no separate table for the tablets; it says the 25 mg tablet trial had side effects similar in type and frequency to the injection table [6].

Why the placebo column matters: the extra risk from the medicine is the gap between the two columns, not the number on the right. On Mounjaro 5 mg, that gap is 3 percentage points; on Zepbound 15 mg it is 15 points [2] [12]. These trials enrolled different people, so the rows do not rank the drugs. Ozempic and Mounjaro figures come from people with type 2 diabetes. Full tables are on the pages for Zepbound, Wegovy, Foundayo, Ozempic and Mounjaro.

How long it lasts

No label gives a number of days. The Zepbound and Mounjaro labels say most nausea, vomiting and diarrhea happened while the dose was being raised and then decreased [13] [15]. The Foundayo label says the same symptoms were more common during its dose-raising period and fell over time [14]. That is why the dose is raised in steps. If diarrhea keeps coming back after each increase, that is worth raising with your prescriber, who can decide whether to slow the schedule.

What helps, according to NIH

MedlinePlus and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) give general advice for diarrhea from any cause. None of it is specific to GLP-1 medicines.

  • Replace fluids. MedlinePlus suggests 8 to 10 glasses of clear fluids a day, plus at least 1 cup of liquid after each loose stool [16]. NIDDK says to replace lost electrolytes as well, for example with broth or sports drinks [21].
  • Check before using rehydration drinks if you have diabetes, kidney disease or another health condition, or if you are older; NIDDK says to talk with a doctor first [22].
  • Eat small meals through the day instead of 3 large ones [17].
  • Skip what makes it worse. MedlinePlus lists fried and greasy foods [18]. NIDDK adds alcohol, drinks with caffeine, and products with sugar alcohols, such as sugarless gum and candy [19] [20].
  • Over-the-counter medicines. NIDDK says loperamide or bismuth subsalicylate is usually safe for short-term diarrhea, but not for people with bloody stools or fever [23]. See a doctor if it gets worse or lasts more than 2 days while you take one [24]. Ask your prescriber or pharmacist before adding any medicine to a GLP-1.

One source does speak to GLP-1 treatment. A 2025 joint advisory from four obesity and nutrition groups (the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society) says avoiding large or high-fat meals can help with diarrhea on these medicines. For significant diarrhea, it says fiber capsules or powders add bulk to the stool and anti-diarrheal medicines can give short-term relief [30]. The FDA labels themselves do not link diarrhea to particular foods.

When to call a doctor

MedlinePlus says adults should contact a provider if diarrhea gets worse or does not improve in 5 days, or if there is blood or mucus in the stool, a fever that does not go away, or ongoing stomach pain [25].

The labels add warnings specific to these medicines:

  • Dehydration and the kidneys. Diarrhea, nausea and vomiting can cause fluid loss that may lead to kidney problems. Drink fluids, and tell your provider right away if the diarrhea does not go away [26]. The Zepbound label reports acute kidney injury, some needing dialysis, after the drug went on sale [27]. In its weight trials, acute kidney injury was reported in 0.5% of people on Zepbound and 0.2% on placebo [28].
  • Pancreatitis. Stop the medicine and call right away for severe stomach pain that will not go away, with or without vomiting, sometimes spreading to the back [29].

Sources

  1. Adverse Reaction Placebo (N=958) % ZEPBOUND 5 mg (N=630) % ZEPBOUND 10 mg (N=948) % ZEPBOUND 15 mg (N=941) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  2. Diarrheaa 8 19 21 23 dailymed.nlm.nih.gov, read Sep 27, 2026.
  3. a Includes diarrhea, frequent bowel movements. dailymed.nlm.nih.gov, read Sep 27, 2026.
  4. Placebo N=1,261 % WEGOVY Injection (2.4 mg Once Weekly) N=2,116 % dailymed.nlm.nih.gov, read Sep 27, 2026.
  5. Diarrhea 16 30 dailymed.nlm.nih.gov, read Sep 27, 2026.
  6. In the clinical trial with WEGOVY 25 mg tablets, the types and frequency of common adverse reactions were similar to those listed in Table 3. dailymed.nlm.nih.gov, read Sep 27, 2026.
  7. Adverse Reaction Placebo (N=1,576) % FOUNDAYO 5.5 mg once daily (N=1,051) % FOUNDAYO 9 mg once daily (N=1,055) % FOUNDAYO 17.2 mg once daily (N=1,049) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  8. Diarrhea 11 21 23 25 dailymed.nlm.nih.gov, read Sep 27, 2026.
  9. Adverse Reaction Placebo (N=262) % OZEMPIC 0.5 mg (N=260) % OZEMPIC 1 mg (N=261) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  10. Diarrhea 1.9 8.5 8.8 dailymed.nlm.nih.gov, read Sep 27, 2026.
  11. Adverse Reaction Placebo (N=235) % MOUNJARO 5 mg (N=237) % MOUNJARO 10 mg (N=240) % MOUNJARO 15 mg (N=241) % dailymed.nlm.nih.gov, read Sep 27, 2026.
  12. Diarrhea 9 12 13 17 dailymed.nlm.nih.gov, read Sep 27, 2026.
  13. The majority of nausea, vomiting, and/or diarrhea events occurred during dose escalation and decreased over time. dailymed.nlm.nih.gov, read Sep 27, 2026.
  14. The incidence of nausea, vomiting, and diarrhea was higher during the FOUNDAYO dosage escalation period and decreased over time. dailymed.nlm.nih.gov, read Sep 27, 2026.
  15. The majority of reports of nausea, vomiting, and/or diarrhea occurred during dose escalation and decreased over time. dailymed.nlm.nih.gov, read Sep 27, 2026.
  16. Drink 8 to 10 glasses of clear fluids every day. Water is best. Drink at least 1 cup (240 milliliters) of liquid every time you have a loose bowel movement. medlineplus.gov, read Sep 27, 2026.
  17. Eat small meals throughout the day, instead of 3 larger meals. medlineplus.gov, read Sep 27, 2026.
  18. You should avoid certain kinds of foods when you have diarrhea, including fried foods and greasy foods. medlineplus.gov, read Sep 27, 2026.
  19. If you have acute diarrhea, avoid foods and drinks that could make diarrhea worse, such as alcoholic beverages. drinks with caffeine, such as coffee, tea, and some soft drinks. niddk.nih.gov, read Sep 27, 2026.
  20. foods and drinks containing sugar alcohols , such as sugarless gum and candies. niddk.nih.gov, read Sep 27, 2026.
  21. When you have diarrhea, you need to replace lost fluids and electrolytes to stay hydrated. Drink plenty of water and liquids that contain electrolytes, such as broths and sports drinks. niddk.nih.gov, read Sep 27, 2026.
  22. Older adults; people with a weak immune system ; and people who have diabetes , kidney disease , or other health conditions should talk with their doctor before drinking oral rehydration solutions. niddk.nih.gov, read Sep 27, 2026.
  23. In most cases, you can safely treat acute diarrhea with over-the-counter medicines such as loperamide and bismuth subsalicylate . Doctors typically recommend against over-the-counter medicines for infants, children, or people who have bloody stools or fever. niddk.nih.gov, read Sep 27, 2026.
  24. See a doctor if your diarrhea gets worse or lasts more than 2 days while taking over-the-counter medicine. niddk.nih.gov, read Sep 27, 2026.
  25. The diarrhea gets worse or does not get better in 2 days for an infant or child, or 5 days for adults Stools with an unusual odor or color Nausea or vomiting Blood or mucus in your stool A fever that does not go away Persisting stomach pain medlineplus.gov, read Sep 27, 2026.
  26. Diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration) which may cause kidney problems. It is important for you to drink fluids to help reduce your chance of dehydration. Tell your healthcare provider right away if you have nausea, vomiting, or diarrhea that does not go away. dailymed.nlm.nih.gov, read Sep 27, 2026.
  27. There have been postmarketing reports of acute kidney injury, in some cases requiring hemodialysis, in patients treated with GLP-1 receptor agonists, or ZEPBOUND dailymed.nlm.nih.gov, read Sep 27, 2026.
  28. In a pool of Study 1 and 2, acute kidney injury was reported in 0.5% of ZEPBOUND-treated patients compared to 0.2% of placebo-treated patients. dailymed.nlm.nih.gov, read Sep 27, 2026.
  29. Stop using ZEPBOUND and call your healthcare provider right away if you have severe pain in your stomach area (abdomen) that will not go away, with or without nausea or vomiting. Sometimes you may feel the pain from your abdomen to your back. dailymed.nlm.nih.gov, read Sep 27, 2026.
  30. Diarrhea can also occur. Avoidance of large or high-fat meals can be helpful. If significant diarrhea occurs, fiber capsules or powders provide bulk to the stool, and anti-diarrheal medications can provide acute relief. pmc.ncbi.nlm.nih.gov, read Sep 28, 2026.

This page reports what official sources say; it is not medical advice. Medical disclaimer.