The most common side effects of GLP-1 medications are digestive: nausea, diarrhea, vomiting and constipation. They tend to show up while the dose is being increased, which is why the labels start low and step up gradually. Most are manageable with smaller meals and enough fluids, but severe or lasting symptoms, or signs of pancreatitis, gallbladder disease, dehydration or an allergic reaction, need to be reported to your prescriber. This guide describes what the labels say and what to log.
This is general information, not medical advice. Talk to your prescriber before changing a dose or stopping a medicine.
How common are the side effects?
The table shows the main digestive reactions in the weight-management trials on the US labels. These are rates from trial populations, not predictions for any one person.
| Reaction | Wegovy 2.4 mg weekly | Placebo (Wegovy trials) | Zepbound 5 / 10 / 15 mg weekly | Placebo (Zepbound trials) |
|---|---|---|---|---|
| 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% |
Sources: Wegovy prescribing information, Table 3; Zepbound prescribing information, Table 1. The two drugs were studied in different trials, so the columns are not a head-to-head comparison.
In the Wegovy trials, 6.8% of people on 2.4 mg stopped the drug because of side effects, against 3.2% on placebo; nausea, vomiting and diarrhea were the leading reasons (Wegovy label, section 6.1). A review of the literature reports that GI effects are generally transient, starting during dose escalation and easing after the maintenance dose is reached (PMC review).
Why they happen
These medicines slow how quickly your stomach empties. Cleveland Clinic explains that this means what you eat, how much and how fast can strongly affect how you feel, and that the stomach has less capacity than before (Cleveland Clinic). That is also why the labels use a gradual schedule: the Wegovy label says to follow the dose escalation to reduce the risk of gastrointestinal reactions, and to consider delaying escalation for 4 weeks if a dose isn’t tolerated (section 2.2). If you want to see how those steps look, our Zepbound dosage schedule and Ozempic timeline guides lay out the label schedules.
Managing nausea, diarrhea and constipation
Cleveland Clinic’s endocrinologist suggests these steps (source):
- Eat lighter in the day before the first shot and avoid a big meal right before a dose.
- Eat smaller, more frequent meals and eat slowly.
- Limit foods that set you off, such as sugary or very fatty foods, ultra-processed snacks and spicy foods.
- Stay hydrated. If drinking with meals makes you feel full, sip between meals, and set reminders if you forget.
- Be careful with fiber right after a dose if you are already bloated, because extra fiber can make symptoms worse. It can still help constipation at other times.
Keep a note of which foods and which days after the shot were worst; it helps your prescriber. If symptoms are heavy or don’t ease, ask about your dose rather than adjusting it yourself.
Dehydration
Vomiting and diarrhea can lead to dehydration. The Wegovy, Ozempic and Zepbound labels all warn of acute kidney injury after dehydration from digestive reactions, and say kidney function should be monitored in people reporting such problems, particularly when starting or increasing a dose (Wegovy label, section 5.5). Call your prescriber if you can’t keep fluids down.
Other effects
Headache, fatigue, dizziness and indigestion also appear in the trial tables: for example, 14% headache and 11% fatigue on Wegovy 2.4 mg versus 10% and 5% on placebo (Wegovy label, Table 3). Hair loss was reported by 3% on Wegovy and 1% on placebo (same table).
Injection site reactions
In the Wegovy weight-management trials, 1.4% of people on the drug and 1% on placebo had injection site reactions such as itching or redness (Wegovy label, section 6.1). In the Zepbound trials, they occurred in 6% to 8% of people on the drug and 2% on placebo (Zepbound label, Table 1). The labels advise rotating injection sites each dose. Report significant pain, swelling or signs of infection.
“Ozempic face” and other cosmetic changes
“Ozempic face” is not a medical term or a drug-specific side effect. Cleveland Clinic describes it as facial volume loss from rapid weight loss, which can also follow bariatric surgery or other fast weight loss. It can bring sunken cheeks, new wrinkles and loose skin, and it is more likely the faster weight comes off. The clinic suggests slower weight loss, enough protein, hydration and a skin care routine, and notes that cosmetic procedures are an option (Cleveland Clinic). If the changes bother you, tell your care team; weight and mood are both worth logging.
Rare or serious problems: when to call your prescriber
The labels list several warnings. Contact your prescriber promptly, or seek urgent care, for:
- Persistent severe abdominal pain, sometimes spreading to the back, with or without vomiting. This can be a sign of pancreatitis, and the Wegovy label says the drug should be stopped if it is suspected (section 5.2).
- Gallbladder symptoms. In the Wegovy adult trials, gallstones were reported in 1.6% on the drug and 0.7% on placebo, and the label notes the risk was higher than placebo even after accounting for weight loss (section 5.3).
- Signs of a serious allergic reaction, such as swelling of the face, lips or throat, or trouble breathing (section 5.7).
- A lump in the neck, trouble swallowing, shortness of breath or persistent hoarseness. Semaglutide and tirzepatide carry a boxed warning about thyroid C-cell tumors (seen in rodents; the human relevance is unknown) and are not for people with a history of medullary thyroid carcinoma or MEN 2.
- Low blood sugar, especially if you also take insulin or a sulfonylurea; the label says dosing of those medicines may need to be reduced.
- Vision changes if you have type 2 diabetes. In a 2-year semaglutide trial, diabetic retinopathy complications occurred more often on the drug than on placebo, with a larger absolute increase in people who already had retinopathy (section 5.8). Tell your prescriber, and ask whether you need eye checks.
- Planned surgery or sedation. The label notes rare reports of pulmonary aspiration during anesthesia or deep sedation in people on GLP-1 drugs, because the drugs delay stomach emptying, and asks patients to tell providers before any planned procedure (section 5.10).
Source for all of the above: Wegovy prescribing information; the Ozempic and Zepbound labels carry equivalent warnings.
What to log
Side effects are easier to manage when you can see when they happen. A useful log includes:
- Injection day, dose and injection site
- Symptoms, severity and time after the shot
- Meals (especially large or fatty ones), protein and fluids
- Weight, measured the same way each week
- Anything you want to ask at the next appointment
Mingo is a GLP-1 tracker for iPhone and Android where you can log shots and doses, food and protein, side effects and weight in one place. It doesn’t replace your doctor or give medical advice. Get the app. For a broader look at treatment goals, see how GLP-1 medications support weight loss.
Key takeaways
- Nausea, diarrhea, vomiting and constipation are the most common effects; rates are in the label tables above.
- They are linked to dose escalation, which is why dosing starts low and rises in steps.
- Smaller meals, slower eating, fluids and avoiding trigger foods are standard first steps.
- Severe abdominal pain, dehydration, allergic symptoms or neck lumps need a prescriber’s attention.
- A log of doses and symptoms makes it easier to decide, together with your prescriber, what to change.
Frequently asked questions
What are common GLP-1 side effects?
Nausea, diarrhea, vomiting, constipation and abdominal pain are the most common, followed by headache, fatigue, indigestion and dizziness. See the table above for the label rates.
How can I reduce nausea from a GLP-1?
Eat smaller meals more slowly, avoid fatty, sugary or spicy foods, don’t take your dose after a large meal, and sip fluids through the day. If nausea is severe or persistent, ask your prescriber about your dose.
Is a GLP-1 safe for long-term use?
The labels describe known risks and warnings, and the WHO’s 2025 guideline notes limited data on long-term efficacy and safety (WHO). Whether long-term use suits you is a decision to make with your prescriber and review regularly.
When do GLP-1 side effects go away?
Digestive effects often ease as your body adjusts, and tend to appear around dose increases, but timing varies by person. If they last or get worse, tell your prescriber.
Can I prevent stomach issues on a GLP-1?
You can lower the odds with gradual dose increases as prescribed, smaller and slower meals, enough fluids and limiting trigger foods. Nobody can promise to prevent them entirely.
