How common the side effects are
The FDA labels for Wegovy (semaglutide) and Zepbound (tirzepatide) report side effects from the weight-management trials. Digestive effects are by far the most common.
| Side effect | Wegovy 2.4 mg | Placebo | Zepbound 5 / 10 / 15 mg | Placebo |
|---|---|---|---|---|
| Nausea | 44% | 16% | 25% / 29% / 28% | 8% |
| Diarrhea | 30% | 16% | 19% / 21% / 23% | 8% |
| Vomiting | 24% | 6% | 8% / 11% / 13% | 2% |
| Constipation | 24% | 11% | 17% / 14% / 11% | 5% |
| Abdominal pain | 20% | 10% | 9% / 9% / 10% | 5% |
| Hair loss | 3% | 1% | 5% / 4% / 5% | 1% |
In Wegovy’s trials, 6.8% stopped the drug because of side effects (3.2% on placebo), most often for nausea, vomiting or diarrhea (Wegovy label, DailyMed). For Zepbound, 4.8% to 6.7% stopped depending on dose (3.4% on placebo), mostly in the first months (Zepbound label, DailyMed). These figures come from the drugs’ pivotal trials, STEP 1 for semaglutide (Wilding et al., NEJM 2021, PMID: 33567185) and SURMOUNT-1 for tirzepatide (Jastreboff et al., NEJM 2022, PMID: 35658024), among others.
This article is general information, not medical advice or a dosing recommendation. Decisions about starting, changing or stopping a prescription belong with a licensed clinician who knows your history.
Serious warnings on the labels
• Thyroid C-cell tumors (boxed warning): both drugs caused these tumors in rodents; whether they do in humans is unknown. Both are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
• Pancreatitis: has occurred; the labels say to stop the drug if pancreatitis is suspected.
• Gallbladder disease: gallstones and gallbladder inflammation occurred in trials.
• Kidney injury: dehydration from vomiting or diarrhea can injure the kidneys.
• Severe digestive reactions: neither drug is recommended with severe gastroparesis; postmarketing reports include ileus and intestinal obstruction.
• Aspiration during anesthesia or deep sedation: both drugs slow stomach emptying; tell the team before any procedure.
• Low blood sugar when combined with insulin or insulin secretagogues such as sulfonylureas, serious allergic reactions, and diabetic retinopathy complications in people with type 2 diabetes; Wegovy’s label also advises monitoring for heart rate increase.
Sources: current Wegovy and Zepbound labels on DailyMed.
Real-world data on rare digestive events
Trials are not large enough to measure rare events well. In a US claims study of people with obesity and no diabetes, GLP-1 drugs used for weight loss (semaglutide or liraglutide) were linked to a higher risk of pancreatitis, bowel obstruction and gastroparesis than bupropion-naltrexone, but not biliary disease. Absolute rates were low, for example pancreatitis at 4.6 per 1,000 person-years for semaglutide (Sodhi et al., JAMA 2023, PMID: 37796527).
What changed in 2025 and 2026
Suicidal thoughts warning removed. After a preliminary review in January 2024 found no evidence that these drugs cause suicidal thoughts, the FDA in January 2026 asked makers of Saxenda, Wegovy and Zepbound to remove the suicidal behavior and ideation warning, citing a comprehensive review that found no increased risk (FDA). Wegovy’s current label lists that warning as removed in February 2026.
NAION, a rare eye condition. In June 2025 the European Medicines Agency’s safety committee concluded that non-arteritic anterior ischemic optic neuropathy, which can cause sudden vision loss, is a very rare side effect of semaglutide (up to 1 in 10,000 people) and that semaglutide should be stopped if it is confirmed (EMA). The current US Wegovy label we checked on October 8, 2026 did not list NAION. Sudden vision loss needs urgent care either way.
Compounded GLP-1s: dosing errors
Compounded semaglutide and tirzepatide are not FDA-approved and come in vials at varying concentrations, often dosed in syringe “units” rather than milligrams. For compounded semaglutide, the FDA has received reports of overdoses, some requiring hospitalization: patients who drew up the wrong amount from a vial took 5 to 20 times the intended dose, and prescribers who miscalculated unit conversions caused doses 5 to 10 times too high (FDA).
If you use a compounded vial, confirm the concentration and the dose in milligrams with your pharmacy. Our dose-to-units calculator shows the math so you can check it against your prescription, not replace it.
Safety: when to get help
• Severe or persistent abdominal pain, with or without vomiting (possible pancreatitis or gallbladder disease)
• Vomiting or diarrhea that stops you keeping fluids down (risk of dehydration and kidney injury)
• A lump or swelling in the neck, trouble swallowing or persistent hoarseness
• Signs of a serious allergic reaction, or sudden changes in vision
Tell your prescriber about pregnancy plans, other diabetes medicines and any upcoming surgery.
This article is general information, not medical advice or a dosing recommendation. Decisions about starting, changing or stopping a prescription belong with a licensed clinician who knows your history.
Comparing GLP-1 providers and costs
Our GLP-1 comparison scores approved partners on real monthly cost, what is included and trust signals; see also GLP-1 cost, GLP-1 with insurance, and our reviews of MEDGm, Found and Luvo Health.
Disclosure
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