The most common side effects of Wegovy and Ozempic (semaglutide) are in the gut: nausea, diarrhea, vomiting, constipation and stomach pain. In the weight-loss trials behind the Wegovy label, 44% of adults on 2.4 mg had nausea, compared with 16% on placebo, and 73% had at least one gut side effect, compared with 47%. The label says these effects were reported most often while the dose was being stepped up, and in the STEP 1 trial they were usually mild to moderate and faded with time. A small number of people get serious problems, such as pancreatitis or gallbladder disease, so it helps to know the warning signs.
Key takeaways
- In Wegovy's weight trials (2,116 adults on 2.4 mg), the most common side effects were nausea (44% vs 16% on placebo), diarrhea (30% vs 16%), vomiting (24% vs 6%) and constipation (24% vs 11%).
- The Wegovy label starts at 0.25 mg once a week and steps up every 4 weeks: 0.5 mg, 1 mg, 1.7 mg, then a maintenance dose from week 17. Gut side effects show up most during these step-ups.
- Severe gut side effects were reported by 4.1% of people on Wegovy injection vs 0.9% on placebo, and 4.3% stopped treatment because of gut side effects vs 0.7%.
- Ozempic is the same medicine, approved for type 2 diabetes, with a top dose of 2 mg. Its gut side effect rates in diabetes trials were lower: 32.7% on 0.5 mg and 36.4% on 1 mg vs 15.3% on placebo.
- Semaglutide has a half-life of about 1 week, so it stays in your body for about 5 to 7 weeks after the last dose.
- Severe stomach pain that will not go away, pain that spreads to your back, yellowing skin or eyes, signs of an allergic reaction, or a lump in your neck need care right away.
What are the most common side effects of Wegovy?
Nausea is the most common side effect of Wegovy, followed by diarrhea, vomiting and constipation. The table below comes from the Wegovy prescribing information. It pools three placebo-controlled trials (STEP 1, 2 and 3) in which adults with obesity or overweight took Wegovy 2.4 mg for up to 68 weeks. It lists side effects reported by at least 2% of people on Wegovy and more often than on placebo.
| Side effect | Wegovy 2.4 mg (n=2,116) | Placebo (n=1,261) |
|---|---|---|
| Nausea | 44% | 16% |
| Diarrhea | 30% | 16% |
| Vomiting | 24% | 6% |
| Constipation | 24% | 11% |
| Stomach (abdominal) pain | 20% | 10% |
| Headache | 14% | 10% |
| Tiredness (fatigue) | 11% | 5% |
| Indigestion (dyspepsia) | 9% | 3% |
| Dizziness | 8% | 4% |
| Bloating (abdominal distension) | 7% | 5% |
| Burping (eructation) | 7% | under 1% |
| Low blood sugar, in people with type 2 diabetes | 6% | 2% |
| Gas (flatulence) | 6% | 4% |
| Stomach flu (gastroenteritis) | 6% | 4% |
| Reflux (GERD) | 5% | 3% |
| Gastritis | 4% | 1% |
| Hair loss | 3% | 1% |
| Skin tingling or sensitivity (dysesthesia) | 2% | 1% |
Many people on placebo also reported nausea, headache and diarrhea, so the gap between the columns is the part linked to the medicine. A percentage counts anyone who had the symptom at any point in the trial, even once. Overall, 6.8% of people on Wegovy stopped because of side effects, compared with 3.2% on placebo.
How do side effects relate to the Wegovy step-ups?
Gut side effects are most likely in the weeks after a dose increase. The Wegovy label says the gradual step-up exists to lower the risk of gut side effects, and that these reactions were reported most often during dose escalation.
| Weeks | Wegovy weekly injection dose on the label |
|---|---|
| 1 to 4 | 0.25 mg (starting dose) |
| 5 to 8 | 0.5 mg |
| 9 to 12 | 1 mg |
| 13 to 16 | 1.7 mg |
| 17 onward | Maintenance dose (2.4 mg recommended, or 1.7 mg) |
The label also says that if a dose is not tolerated during the step-up, the prescriber can consider waiting another 4 weeks before the next increase. The current US label also lists a higher 7.2 mg weekly dose (sold as Wegovy HD) for some adults who have tolerated 2.4 mg for at least 4 weeks. In those trials, nausea was reported by 39% on 7.2 mg, 35% on 2.4 mg and 13% on placebo, and skin tingling or sensitivity by 22%, 6% and 0%.
Your prescriber decides your dose and the pace of your step-ups. If side effects feel hard to manage, tell them before your next shot. You can see the label schedules side by side in our titration schedules tool.
How long do Wegovy side effects last?
For most people, gut side effects are worst in the first days after a shot and in the weeks after each step-up, then ease. The STEP 1 trial in the New England Journal of Medicine described nausea and diarrhea as typically temporary, mild to moderate, and fading with time.
There is no single number for how long it lasts. Common patterns:
- Around shot day. Many people notice nausea or fullness in the first days after the injection, then feel better later in the week.
- After each step-up. Symptoms can return for a week or two when the dose goes up, even if the previous dose felt fine.
- At maintenance. Once the dose is stable, symptoms often settle. Constipation can hang on longer than nausea for some people.
Because semaglutide has a half-life of about 1 week, the label notes it stays in your body for about 5 to 7 weeks after the last dose. That is one reason side effects do not switch off the moment a dose changes.
What helps with nausea, constipation and other side effects?
Small changes to how you eat help many people. These are general habits, not a treatment plan.
- Eat smaller meals, slower. Semaglutide slows how fast your stomach empties, so a normal-sized plate can feel like too much. Stop when you feel satisfied, not full.
- Go easy on greasy and very rich food, especially in the days after your shot. Many people find fatty meals make nausea and burping worse.
- Drink steadily through the day. Vomiting and diarrhea can dehydrate you, and the label warns that dehydration has led to kidney problems. Our water calculator gives you a daily target.
- For constipation, add fiber and fluids together. Fiber without enough water can make things worse. Movement helps too.
- Keep protein in each meal. It helps you eat enough on days with a small appetite.
Ask your clinician or pharmacist before taking anything for these symptoms. Semaglutide slows stomach emptying, which can change how some pills are absorbed.
What are the serious warnings on the Wegovy and Ozempic labels?
Serious side effects are uncommon, but the labels list them clearly. Contact your clinician or seek care if you notice any of these:
- Pancreatitis. Severe stomach pain that will not go away, sometimes spreading to your back, with or without vomiting. The label says to stop the medicine and get checked if pancreatitis is suspected.
- Gallbladder problems. In Wegovy's adult weight trials, gallstones were reported by 1.6% vs 0.7% on placebo. Signs include pain in the upper right belly, fever, yellowing of the skin or eyes, and clay-colored stools.
- Severe dehydration and kidney problems. Vomiting or diarrhea that will not stop, very little urine, or dizziness when standing.
- Allergic reactions. Swelling of the face, lips, tongue or throat, trouble breathing or swallowing, severe rash, or fainting. Seek emergency care.
- Thyroid tumors. Both labels carry a boxed warning: semaglutide caused thyroid C-cell tumors in rodents, and it is not known whether it does in people. Tell your clinician about a lump or swelling in your neck, trouble swallowing, shortness of breath, or hoarseness that does not go away. People with a personal or family history of medullary thyroid cancer or MEN 2 should not use it.
- Low blood sugar if you also take insulin or a sulfonylurea. Signs include shakiness, sweating, confusion and a fast heartbeat.
- Diabetic eye changes in people with type 2 diabetes, and a faster heart rate (on average 1 to 4 beats per minute). Report vision changes or a heart that races at rest.
- Surgery and sedation. Tell every care team that you take semaglutide before any procedure, because food can stay in the stomach longer.
If you have severe stomach pain that will not go away, signs of an allergic reaction, or cannot keep fluids down, contact your clinician or seek urgent care. Do not wait for your next appointment.
How are Ozempic side effects different?
Ozempic is the same medicine as Wegovy, semaglutide, but it is approved for adults with type 2 diabetes, not for weight management. Its label starts at 0.25 mg weekly for 4 weeks, then 0.5 mg, with steps to 1 mg and a maximum of 2 mg if more blood sugar control is needed.
Side effects are the same type, but the rates in Ozempic's diabetes trials were lower than in Wegovy's weight trials, which used higher doses in a different group of patients.
| Side effect (Ozempic diabetes trials) | Placebo | Ozempic 0.5 mg | Ozempic 1 mg |
|---|---|---|---|
| Nausea | 6.1% | 15.8% | 20.3% |
| Vomiting | 2.3% | 5% | 9.2% |
| Diarrhea | 1.9% | 8.5% | 8.8% |
| Stomach pain | 4.6% | 7.3% | 5.7% |
| Constipation | 1.5% | 5% | 3.1% |
In a trial comparing doses, gut side effects were reported by 34% on 2 mg and 30.8% on 1 mg. Low blood sugar matters more on Ozempic, because many people take it with other diabetes medicines. The US also now has Ozempic tablets, taken daily for type 2 diabetes.
What about the Wegovy pill?
In the US, Wegovy also comes as a once-daily tablet for weight management and heart risk reduction in adults. The label starts it at 1.5 mg a day for 30 days, then 4 mg, then 9 mg, reaching a 25 mg maintenance dose from day 91. It is taken in the morning on an empty stomach with up to 4 ounces (120 mL) of water, and you wait at least 30 minutes before eating, drinking or taking other pills.
In its 64-week trial, the label says common side effects were similar in type and frequency to the injection. Severe gut side effects were reported by 2% on the tablet vs 0% on placebo, and 3.4% stopped because of gut side effects vs 2%. Average weight change was 13.6% on the tablet vs 2.4% on placebo.
How Morning helps
Morning keeps a shot log with the dose plan you and your clinician set, and side-effect check-ins that show whether your nausea or constipation clusters around shot day or after a step-up. The food photo scan counts protein, fiber and water toward your daily targets, which matters most on low-appetite days. Before appointments, the doctor report puts your shots, symptoms and weight on one page so the conversation with your clinician starts from facts.
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Questions
How long does nausea last on Wegovy?
For most people, nausea is strongest in the first days after a shot and in the weeks after a dose increase, then eases. The STEP 1 trial described it as usually mild to moderate and fading with time. If it does not ease, or you cannot keep fluids down, contact your clinician.
Are Ozempic side effects the same as Wegovy?
They are the same type, because both are semaglutide. Ozempic's label reports lower rates, for example nausea in 15.8% to 20.3% of people in diabetes trials vs 44% on Wegovy 2.4 mg in weight trials, mostly because of the lower doses and different patients.
Does Wegovy cause hair loss?
In Wegovy's 2.4 mg weight trials, hair loss was reported by 3% of people vs 1% on placebo. It was more common at 7.2 mg (5.8%) and in women. Mention it to your clinician if you notice it.
When should I call my doctor about Wegovy side effects?
Call your clinician or seek care for severe stomach pain that will not go away, pain spreading to your back, vomiting or diarrhea that stops you keeping fluids down, yellowing skin or eyes, signs of an allergic reaction, or a lump in your neck. For milder side effects that do not ease, ask before your next shot.
Sources
- Wegovy (semaglutide) injection and tablets, US prescribing information, DailyMed
- Ozempic (semaglutide) injection, US prescribing information, DailyMed
- Rybelsus and Ozempic (semaglutide) tablets, US prescribing information, DailyMed
- Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989-1002
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Educational information, not medical advice. Talk to your clinician about your treatment.