GLP-1 Side Effects: What to Expect
What FDA labels report, when side effects tend to show up, what may help, and which symptoms need medical care.
Last updated
Side effects are one of the first things people ask about, and for good reason. This page summarizes what FDA labels and public guidance say. It can’t tell you what you’ll experience, because that varies from person to person. Your clinician knows your health history, so bring your questions to them.
Common side effects
Digestive side effects are the most common. In adult weight management trials, 73% of people on semaglutide injection and 47% on placebo reported one. For tirzepatide, it was 56% at each studied dose and 30% on placebo. So some people had these symptoms without the medication too.
Share of adults reporting each side effect in trials, from FDA labeling. Trials differ, so don’t compare the two medications directly.
| Side effect | SemaSemaglutide 2.4 mg injection | Placebo | TirzTirzepatide, by dose | Placebo |
|---|---|---|---|---|
| Nausea | 44% | 16% | 25–29% | 8% |
| Diarrhea | 30% | 16% | 19–23% | 8% |
| Vomiting | 24% | 6% | 8–13% | 2% |
| Constipation | 24% | 11% | 11–17% | 5% |
| Abdominal pain | 20% | 10% | 9–10% | 5% |
Sema: semaglutide 2.4 mg injection. Tirz: tirzepatide, by dose. Each Placebo column is the comparison group for the medication to its left.
The labels also list others, including indigestion, burping, gas, bloating, reflux, fatigue, dizziness, and hair loss. Headache is listed for semaglutide, and injection site reactions for tirzepatide.
Why doses start low and rise slowly
Both labels start at a low dose and step up gradually to reduce the risk of digestive side effects. The joint advisory says gradual dose escalation helps the body adjust.
- Semaglutide injection starts with 4 weeks at the lowest dose, then rises every 4 weeks to a maintenance dose at about week 17.
- Tirzepatide starts with 4 weeks at the lowest dose before the first increase.
If a dose isn’t tolerated, the semaglutide label says a clinician may consider delaying the next increase. Don’t change your dose or schedule on your own. Your clinician sets it.
A general timeline
Labels and trials describe a broad pattern. They don’t give an exact timeline, and we won’t guess at one.
Early weeks
The joint advisory says side effects are more likely in the first weeks after starting. It notes that nausea often occurs in the morning or after longer periods without eating.
During dose increases
Symptoms can come back or start when a dose goes up. The tirzepatide label says the majority of nausea, vomiting, and diarrhea events occurred during dose escalation and decreased over time.
On a stable dose
The advisory says side effects tend to decrease in frequency and severity with a stable dose. That’s a general pattern, so it may not match your experience. If symptoms don’t go away, tell your clinician.
Comfort tips
These come from the joint advisory and Cleveland Clinic. They’re general ideas, so ask your clinician what fits you.
- Eat smaller meals. Smaller, more frequent meals can help, but that doesn’t mean skipping meals.
- Slow down. Your brain can take time to register fullness, so pacing yourself helps you stop when you’ve had enough.
- Limit trigger foods. Avoiding large or high-fat meals can help. So can cutting back on greasy, sugary, or spicy foods.
- Stay hydrated. Drink fluids through the day. If drinking at meals makes you too full, sip between meals.
- Keep alcohol minimal. It may worsen nausea and reflux.
- For constipation, fluids and fiber from foods can help, and your clinician can suggest other options.
- Ask about medication. Your clinician may suggest options for nausea or diarrhea, or a change to your dosing plan.
Serious risks in the labels
These are less common, but you should know them. The list below comes from the semaglutide and tirzepatide labels and may not be complete, so read the Medication Guide that comes with any prescription.
Thyroid C-cell tumors (boxed warning)
Both labels carry the FDA’s boxed warning. These medications caused thyroid tumors in rodents, and it isn’t known whether they do in people. They shouldn’t be used by anyone with a personal or family history of medullary thyroid carcinoma, or with MEN 2. Tell your clinician about a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath.
Pancreatitis
This is inflammation of the pancreas, and it can be fatal. The Medication Guide says to stop the medication and call your provider right away for severe stomach pain that won’t go away, with or without vomiting. The pain may reach your back.
Gallbladder problems
Both labels report more gallbladder disease with treatment, including gallstones, and some cases need surgery. Call your provider about upper stomach pain, yellowing skin or eyes, fever, or clay-colored stools.
Low blood sugar with other medications
The risk is higher with insulin or a sulfonylurea, and those doses may need adjusting. Signs include dizziness, sweating, shakiness, and confusion. Tell your clinician about every medication you take.
Kidney problems from dehydration
Both labels report acute kidney injury, mostly in people dehydrated by nausea, vomiting, or diarrhea. Some cases needed dialysis. Tell your provider right away if those symptoms don’t go away.
Severe stomach problems
Digestive side effects can be severe, and neither medication is recommended for people with severe gastroparesis.
Other label warnings
The labels also cover vision changes in people with type 2 diabetes. They warn that food can be inhaled into the lungs during anesthesia or deep sedation, so tell your care team before any surgery or procedure. For pregnancy and birth control, see our under 35 guide.
When to get emergency care
Call 911 or go to the nearest emergency room for trouble breathing or swallowing, swelling of your face, lips, tongue, or throat, fainting, or severe symptoms that worry you. These can be signs of a serious allergic reaction. The labels say to stop the medication and get help.
Orforglipron: what the label says
Orforglipron (Foundayo) is a once-daily pill. Everything above comes from the semaglutide and tirzepatide labels and public guidance. This section comes from the orforglipron label (PDF), revised July 2026, and the symptom lists in Lilly’s safety summary. Your experience may differ.
Common side effects of orforglipron
Digestive side effects were reported by 60–69% of people on orforglipron, depending on dose, and 37% on placebo (PDF). The label says nausea, vomiting, and diarrhea were more common during dose increases and decreased over time.
Share of adults reporting each side effect in two trials of up to 72 weeks, from the orforglipron label. Stomach pain, feeling tired, and hair loss include related terms. Trials differ, so don’t compare these numbers with the semaglutide or tirzepatide table.
| Side effect | 5.5 mg | 9 mg | 17.2 mg | Placebo |
|---|---|---|---|---|
| Nausea | 26% | 34% | 35% | 10% |
| Constipation | 20% | 27% | 24% | 9% |
| Diarrhea | 21% | 23% | 25% | 11% |
| Vomiting | 13% | 21% | 24% | 4% |
| Indigestion | 12% | 16% | 13% | 4% |
| Stomach pain | 13% | 14% | 14% | 7% |
| Headache | 8% | 9% | 9% | 7% |
| Swollen belly | 7% | 9% | 8% | 3% |
| Feeling tired | 6% | 7% | 9% | 4% |
| Belching | 6% | 8% | 8% | 1% |
| Reflux | 6% | 6% | 7% | 2% |
| Gas | 5% | 6% | 6% | 2% |
| Hair loss | 4% | 4% | 5% | 2% |
The label’s safety data comes from adults with an average age of 49, so rates for younger adults may differ.
The label says 8% of people on orforglipron stopped because of side effects, compared with 3% on placebo. These aren’t all the possible side effects.
Serious risks of orforglipron
- Thyroid C-cell tumors (boxed warning): The label carries a boxed warning. Similar medications caused thyroid tumors in rodents. Orforglipron isn’t active in rats or mice and didn’t cause tumors in them, and it isn’t known what these findings mean for people. The label still warns about a potential risk of medullary thyroid carcinoma. It says not to use orforglipron if you or any of your family have had that cancer, or if you have MEN 2. Tell your provider about a neck lump or swelling, hoarseness, trouble swallowing, or shortness of breath.
- Pancreatitis: Lilly says to stop taking it and call your provider right away for severe stomach pain that won’t go away, with or without nausea or vomiting.
- Severe stomach problems: Tell your provider about stomach problems that are severe or won’t go away.
- Dehydration and kidney problems: Fluid loss from diarrhea, nausea, or vomiting may cause kidney problems. Tell your provider right away if those symptoms don’t go away.
- Low blood sugar: The risk may be higher with insulin or a sulfonylurea.
- Serious allergic reactions: Lilly says to stop using it and get medical help right away for swelling of your face, lips, tongue, or throat, problems breathing or swallowing, severe rash or itching, fainting, or very rapid heartbeat.
- Gallbladder problems: Tell your provider right away about upper stomach pain, fever, yellowing skin or eyes, or clay-colored stools.
- Vision changes: People with type 2 diabetes should tell their provider about changes in vision.
- Surgery and sedation: Tell your care team you take it before any procedure that uses anesthesia or deep sedation.
The label also says it may cause fetal harm and should be stopped when a pregnancy is recognized, and it advises effective contraception during treatment. It says orforglipron isn’t recommended while breastfeeding or with other GLP-1 medications. Talk to a licensed provider about what applies to you.
More from the orforglipron label
The label (PDF) also covers these points. Talk to a licensed provider about how they apply to you.
- Low blood pressure: It was reported by 2% of people on orforglipron and 0.5% on placebo. It was more common in people also taking blood pressure medication.
- Fast heart rate: It was reported by 3% of people on orforglipron and 0.9% on placebo. Heart rate rose by an average of 4–5 beats per minute, compared with 0.5 on placebo.
- Other medications: The label says not to take more than 20 mg of simvastatin a day with orforglipron. Some other medications can raise or lower orforglipron levels, which can limit your dose or rule out using them together. Because orforglipron slows stomach emptying, it may also affect how other pills are absorbed. Give your provider a full list of what you take.
- Liver problems: It isn’t recommended for people with severe liver impairment.
- Missed doses: The label says to take a missed dose as soon as possible and not to double up. After 7 or more missed doses in a row, it says to restart at a lower dose, so check with your provider before you take your next one.
Compounded products: added concerns
Compounded medications are not FDA-approved, and they aren’t the same as FDA-approved products. The FDA doesn’t review them for safety, effectiveness, or quality before they’re marketed. The FDA’s page on unapproved GLP-1s lists these concerns:
- Dosing errors. People have measured the wrong dose, and some clinicians have miscalculated, with some reports requiring hospitalization.
- Doses beyond the label. The FDA has reports tied to prescribed doses above FDA-approved labeling.
- Handling. Multi-dose vials can raise contamination concerns, and some products have reportedly arrived warm.
- Fraud. Some products carry false label information, sometimes naming pharmacies that don’t exist.
- Under-reporting. As of May 31, 2026, the FDA had 990 reports linked to compounded semaglutide and more than 730 to compounded tirzepatide. It says the real number is likely higher, and that it can’t always tell whether the drug caused an event.
Our guide to how access works explains compounded options and how to check a pharmacy.
Questions to ask your clinician
Frequently asked questions
What are the most common GLP-1 side effects in the first month?
Digestive side effects are the most common, including nausea, diarrhea, vomiting, and constipation. A joint advisory from four professional groups says side effects are more likely in the first weeks and with dose increases. Not everyone gets them. Ask your clinician what to expect.
How long do GLP-1 side effects last?
It varies, and the labels do not give a set number of days. The tirzepatide label says most nausea, vomiting, and diarrhea happened during dose increases and decreased over time. Tell your clinician if symptoms don’t go away.
What helps with GLP-1 nausea?
Published guidance includes eating smaller meals, avoiding large or high-fat meals, eating slowly, and drinking enough fluids. Alcohol may make nausea and reflux worse. Ask your clinician about other options, including whether your dose schedule should change.
When should I call a clinician about side effects?
Call right away for severe stomach pain that won’t go away, or for nausea, vomiting, or diarrhea that doesn’t stop. Also call about upper stomach pain, yellowing skin or eyes, or a lump in your neck. Get emergency help for trouble breathing or swelling of your face or throat.
Are side effects different with compounded products?
The FDA says many reported events appear consistent with those of FDA-approved drugs, but it also reports dosing errors and other concerns specific to compounded products. Compounded medications are not FDA-approved. The FDA does not review them for safety, effectiveness, or quality before they are marketed.
See our full FAQ for more, our costs page for budgeting, or compare programs and how they handle follow-up care.
Sources
We read each of these pages on November 1, 2026. Rules and labeling change, so check the source for the current version.
- Semaglutide injection and tablets prescribing information. DailyMed, U.S. National Library of Medicine, revised June 2026.
- Tirzepatide injection prescribing information. DailyMed, U.S. National Library of Medicine, revised August 2026.
- Orforglipron tablets prescribing information (PDF). Eli Lilly and Company, revised July 2026.
- Orforglipron safety summary. Eli Lilly and Company, on LillyDirect, April 2026, checked November 1, 2026.
- Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory. American College of Lifestyle Medicine, American Society for Nutrition, Obesity Medicine Association, and The Obesity Society. Obesity Pillars, 2026.
- How To Manage the Digestive Side Effects of GLP-1 Medications. Cleveland Clinic Health Essentials, September 9, 2026.
- FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. U.S. Food and Drug Administration, current as of October 1, 2026.
- Compounding and the FDA: Questions and Answers. U.S. Food and Drug Administration, current as of September 16, 2025.