Guides / Side effects and results

GLP-1 side effects: how common and how long they last

Stomach trouble tops the side-effect list on every GLP-1 label, and most of it happens while the dose is going up.

By PeptideTracker editorial team · Updated November 8, 2026 · 7 sources

[00] Short answer

  1. Nausea is the most common GLP-1 side effect. It was reported by 44% of adults on Wegovy 2.4 mg vs 16% on placebo, and by 25–29% on Zepbound vs 8%1–2.
  2. Most nausea, vomiting and diarrhea happens while the dose is being increased, and lessens over time2,4.
  3. In the STEP 1–3 trials of semaglutide 2.4 mg, a typical bout of nausea lasted 8 days, diarrhea 3 days and vomiting 2 days. Constipation lasted longer, a median of 47 days6.
  4. Severe stomach pain that won't go away, sometimes reaching your back, can be a sign of pancreatitis. The labels say to stop the medicine and call your provider right away1.

How common are GLP-1 side effects?

GLP-1 side effects are common, and most are in the stomach and gut. On Wegovy 2.4 mg, 73% of adults in the weight-loss trials reported a stomach or gut side effect, compared with 47% on placebo1. On Zepbound, it was 56% at every dose (5 mg, 10 mg and 15 mg) vs 30% on placebo2.

Percent of adults reporting each side effect: weight-management trials (US labels, section 6.1)
GroupNauseaDiarrheaVomitingConstipation
Wegovy placebo116%16%6%11%
Wegovy 2.4 mg weekly144%30%24%24%
Zepbound placebo28%8%2%5%
Zepbound 5 mg weekly225%19%8%17%
Zepbound 10 mg weekly229%21%11%14%
Zepbound 15 mg weekly228%23%13%11%
Foundayo placebo510%11%4%9%
Foundayo 5.5 mg daily526%21%13%20%
Foundayo 9 mg daily534%23%21%27%
Foundayo 17.2 mg daily535%25%24%24%

Wegovy: 68-week trials, Table 3. Zepbound: 72-week trials, Table 1. Foundayo: 72-week trials, Table 11–2,5. Compare each medicine with its own placebo row.

Each label warns that side-effect rates from one drug's trials "cannot be directly compared" to rates in another drug's trials1–2. The people, doses and trial lengths differ, which is why each medicine has its own placebo row.

  • On Wegovy 7.2 mg, nausea was 39%, vomiting 22% and constipation 20%, compared with 35%, 16% and 19% on 2.4 mg in the same trials1.
  • Stopping because of side effects: 6.8% on Wegovy 2.4 mg vs 3.2% on placebo1. On Zepbound, 1.9% to 4.3% stopped because of stomach side effects vs 0.5% on placebo2.

Side effects on Ozempic and Mounjaro (diabetes doses)

In the type 2 diabetes trials, nausea was reported by 15.8% to 20.3% of people on Ozempic 0.5 mg to 1 mg, and by 12% to 18% on Mounjaro 5 mg to 15 mg3–4. The rates rise with the dose for both medicines.

Percent of adults with type 2 diabetes reporting each side effect (US labels, Table 1)
GroupNauseaDiarrheaVomitingConstipation
Ozempic placebo36.1%1.9%2.3%1.5%
Ozempic 0.5 mg315.8%8.5%5%5%
Ozempic 1 mg320.3%8.8%9.2%3.1%
Mounjaro placebo44%9%2%1%
Mounjaro 5 mg412%12%5%6%
Mounjaro 10 mg415%13%5%6%
Mounjaro 15 mg418%17%9%7%

Overall, stomach and gut side effects were reported by 32.7% (0.5 mg) and 36.4% (1 mg) on Ozempic vs 15.3% on placebo3, and by 37.1% to 43.6% on Mounjaro vs 20.4% on placebo4. These rates are lower than in the weight trials above, but the trials enrolled different people.

When do GLP-1 side effects start and how long do they last?

GLP-1 stomach side effects mostly happen while the dose is being stepped up. The Zepbound and Mounjaro labels say most nausea, vomiting and diarrhea happened while the dose was going up (dose escalation), and eased over time2,4. Ozempic and Wegovy say the same about the dose-increase period1,3.

  • How long each bout lasts (semaglutide 2.4 mg): in the pooled STEP 1–3 trials, the median length of a bout was 8 days for nausea, 3 days for diarrhea and 2 days for vomiting. Constipation lasted longer, a median of 47 days (35 days on placebo)6.
  • When they peak: in those trials, nausea, diarrhea and vomiting were most common around week 20, just after people reached the 2.4 mg dose at week 16, and fell after that6.
  • How severe: 98.1% of the stomach side effects on semaglutide 2.4 mg were mild to moderate, and 4.3% of people stopped treatment because of them6.
  • Tirzepatide: across SURMOUNT-1 to -4, stomach side effects happened mainly during the 20-week dose-increase period. When people needed medicine for diarrhea or sickness, they most often first used it in the first 24 weeks7.

Because side effects cluster around dose increases, the labels build in slow steps. Wegovy says that if a dose isn't tolerated during the increases, the next step can be delayed by 4 weeks1. That decision is made with your prescriber.

Other common GLP-1 side effects: hair loss, tiredness, skin sensations

Besides stomach effects, the Wegovy and Zepbound labels list tiredness, dizziness, hair loss and burping among the common side effects. Hair loss was reported by 3% on Wegovy 2.4 mg vs 1% on placebo, and by 4% to 5% on Zepbound vs 1%1–2.

  • Tiredness: 11% on Wegovy 2.4 mg vs 5% on placebo1; 5% to 7% on Zepbound vs 3%2.
  • Injection site reactions: 6% to 8% on Zepbound vs 2% on placebo2.
  • Changes in skin sensation (tingling, burning or sensitive skin, called dysesthesia): 2% on Wegovy 2.4 mg in the main trials, and 22% on Wegovy 7.2 mg vs 6% on 2.4 mg in the 7.2 mg trials1.
  • Low blood sugar: more likely if you also take insulin or a sulfonylurea for diabetes1–2.

Serious GLP-1 warnings on the label

Every GLP-1 label in this guide carries a boxed warning about thyroid C-cell tumors. Semaglutide and tirzepatide caused these tumors in rodents, and it is not known whether they cause them in people1–4. Foundayo's warning is worded differently. Orforglipron isn't active in rats or mice and didn't cause tumors in them, so its warning is based on other GLP-1 medicines5. The labels say not to use these medicines if you or a family member has had medullary thyroid carcinoma (MTC), or if you have MEN 21–2,5.

  • Pancreatitis: in the Wegovy weight trials, it was confirmed in 4 people on Wegovy (0.2 cases per 100 patient-years) and 1 on placebo1. In the Zepbound weight trials, 0.2% on Zepbound and 0.2% on placebo2.
  • Gallbladder problems: gallstones in 1.6% on Wegovy vs 0.7% on placebo1, and in 1.1% on Zepbound vs 1% on placebo. Gallbladder inflammation was 0.7% on Zepbound vs 0.2%2.
  • Dehydration and kidney problems: fluid loss from vomiting or diarrhea can lead to kidney problems1–2.
  • Severe stomach problems: reported by 4.1% on Wegovy vs 0.9% on placebo1.
  • Serious allergic reactions, vision changes in people with type 2 diabetes, and food getting into the lungs during anesthesia or deep sedation are also listed1–2.

When to call your doctor about GLP-1 side effects

Call your prescriber or a doctor right away about severe stomach pain that won't go away, with or without vomiting. The Wegovy Medication Guide says to stop the medicine too, and that the pain may spread to your back1. The Zepbound label gives the same advice2.

  • Gallbladder symptoms: pain in the upper stomach, yellow skin or eyes, fever, or clay-colored stools1.
  • Nausea, vomiting or diarrhea that doesn't go away: tell your provider right away. The Medication Guide says to drink fluids to lower the chance of dehydration1.
  • Signs of a serious allergic reaction: swelling of the face, lips, tongue or throat, trouble breathing or swallowing, severe rash, fainting or a very fast heartbeat. Stop the medicine and get medical help right away1.
  • A lump or swelling in the neck, hoarseness, trouble swallowing or shortness of breath1.
  • Changes in vision if you have type 2 diabetes, or a racing or pounding heartbeat at rest that lasts several minutes1.
  • Before surgery or a procedure with anesthesia or deep sedation, tell the team you take a GLP-11–2.

Questions

How long does GLP-1 nausea last?

In the STEP 1–3 trials of semaglutide 2.4 mg, the median bout of nausea lasted 8 days. Nausea was most common around week 20, just after the top dose was reached, and became less common after that.

Do GLP-1 side effects go away?

Nausea, vomiting and diarrhea usually ease. The Zepbound and Mounjaro labels say most of it happened during dose increases and decreased over time. Tell your provider about any side effect that bothers you or doesn't go away.

Is constipation on a GLP-1 different from nausea?

Yes. In the semaglutide 2.4 mg trials, a bout of constipation lasted a median of 47 days, much longer than nausea (8 days). It was reported by 24% on Wegovy 2.4 mg vs 11% on placebo.

Does a higher dose mean more side effects?

For nausea, the labels show a rise with dose. On Mounjaro, nausea went from 12% at 5 mg to 18% at 15 mg, and on Ozempic from 15.8% at 0.5 mg to 20.3% at 1 mg. Not every side effect rises: on Zepbound, constipation was 17% at 5 mg and 11% at 15 mg.

Does hair loss happen on Wegovy or Zepbound?

Hair loss is listed on the Wegovy and Zepbound labels. It was reported by 3% on Wegovy 2.4 mg vs 1% on placebo, and 4% to 5% on Zepbound vs 1%.

Do GLP-1 side effects come back after a missed dose?

The Wegovy label says that after 2 or more missed doses in a row, your prescriber may restart the dose increases at a lower dose to reduce the risk of stomach side effects. See our missed-dose guide for each medicine's rule.

Sources

Checked against Wegovy, Zepbound, Ozempic, Mounjaro and Foundayo US prescribing information and Medication Guides (2026), and pooled STEP and SURMOUNT tolerability analyses (Diabetes Obes Metab). How we check

  1. 1Wegovy (semaglutide) injection and tablets, US prescribing information and Medication Guide, sections 2.2, 5, 6.1 and 17. Novo Nordisk, revised 06/2026; Tables 3 and 4
  2. 2Zepbound (tirzepatide) US prescribing information, sections 5, 6.1 and 17. Eli Lilly, revised 08/2026; Table 1
  3. 3Ozempic (semaglutide) injection, US prescribing information, sections 5 and 6.1. Novo Nordisk, revised 05/2026; Table 1
  4. 4Mounjaro (tirzepatide) US prescribing information, sections 5 and 6.1. Eli Lilly, revised 08/2026; Table 1
  5. 5Foundayo (orforglipron) tablets, US prescribing information, sections 5 and 6. Eli Lilly, revised 07/2026; Table 1
  6. 6Wharton S, et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity. Diabetes Obes Metab 2022;24:94-105. doi:10.1111/dom.14551; results section 3.3
  7. 7Rubino DM, et al. Gastrointestinal tolerability and weight reduction associated with tirzepatide in the SURMOUNT-1 to -4 trials. Diabetes Obes Metab 2025;27:1826-1835. doi:10.1111/dom.16176

This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.

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