Quick answer: the most common semaglutide side effects are nausea, diarrhea, vomiting and constipation. On Wegovy 2.4 mg, 44% of adults had nausea, 30% diarrhea and 24% each vomiting and constipation, compared with 6% to 16% on placebo; on Ozempic, nausea affected 16% to 20%.[1][2] Most episodes are mild to moderate and short, and they cluster around dose increases.[3]
Semaglutide is sold as Ozempic (type 2 diabetes), Wegovy (weight loss, heart risk and liver disease) and Rybelsus (diabetes tablet). This guide uses the Ozempic and Wegovy labels. For more on the drug, see our semaglutide profile and how the brands differ in Wegovy vs Ozempic.
Semaglutide side effects on Wegovy and Ozempic
| Side effect | Wegovy 2.4 mg (placebo) | Ozempic 0.5 mg / 1 mg (placebo) |
|---|---|---|
| Nausea | 44% (16%) | 15.8% / 20.3% (6.1%) |
| Diarrhea | 30% (16%) | 8.5% / 8.8% (1.9%) |
| Vomiting | 24% (6%) | 5.0% / 9.2% (2.3%) |
| Constipation | 24% (11%) | 5.0% / 3.1% (1.5%) |
| Abdominal pain | 20% (10%) | 7.3% / 5.7% (4.6%) |
| Headache | 14% (10%) | Not in main table |
| Fatigue | 11% (5%) | Not in main table |
| Indigestion | 9% (3%) | 3.5% / 2.7% (1.9%) |
| Dizziness | 8% (4%) | Not in main table |
| Burping | 7% (under 1%) | 2.7% / 1.1% (0%) |
| Reflux (GERD) | 5% (3%) | 1.9% / 1.5% (0%) |
| Hair loss | 3% (1%) | Not in main table |
Sources: Wegovy and Ozempic prescribing information.[1][2]
Wegovy was tested at a higher dose in people with obesity; Ozempic at lower doses in people with type 2 diabetes. That explains most of the gap, so these columns are not a head-to-head comparison.
How side effects change with dose
Stomach side effects rise with dose. In the trials of the newer Wegovy 7.2 mg dose, nausea affected 39% and vomiting 22%, versus 35% and 16% on 2.4 mg and 13% and 6% on placebo.[1] Altered skin sensations, such as tingling, burning or sensitive skin (dysesthesia), jumped from 6% on 2.4 mg to 22% on 7.2 mg.[1] Hair loss rose from 3% to 6%.[1]
On Ozempic, stomach side effects affected 34% of people on 2 mg versus 30.8% on 1 mg.[2] The label escalation schedules start low for this reason: Wegovy begins at 0.25 mg for 4 weeks and steps up every 4 weeks, and if a step is not tolerated the label suggests delaying the next increase by 4 weeks.[1] See our semaglutide dosage chart.
When side effects start and how long they last
In a pooled analysis of the STEP 1 to 3 trials (about 3,400 adults), stomach side effects on semaglutide 2.4 mg were 98.1% mild to moderate and occurred most often during or shortly after dose escalation.[3]
- Nausea: median episode of 8 days.[3]
- Diarrhea: median of 3 days.[3]
- Vomiting: median of 2 days.[3]
- Constipation: longer, with a median of 47 days (35 days on placebo).[3]
In STEP 1, nausea and diarrhea were typically transient and subsided with time, and 4.5% of people on semaglutide stopped because of stomach side effects, versus 0.8% on placebo.[4] Weight loss was similar whether or not people had stomach side effects, so feeling sick is not a sign the drug is working better.[3]
Our detailed guides cover GLP-1 nausea, semaglutide heartburn and Ozempic breath.
Other semaglutide side effects
- Fatigue and headache were more common than on placebo on Wegovy (11% vs 5%, and 14% vs 10%).[1]
- Faster heart rate: an average rise of 1 to 4 beats per minute on Wegovy.[1]
- Low blood pressure and fainting: 1.3% and 0.8% on Wegovy, versus 0.4% and 0.2% on placebo, sometimes linked to fluid loss from stomach side effects.[1]
- Gallstones: 1.6% on Wegovy injection versus 0.7% on placebo, and 2.5% on Wegovy tablets versus 1%.[1] Teenagers had a higher rate (3.8%).[1]
- Appendicitis: 0.5% versus 0.2% on placebo.[1]
- Fractures: in the heart outcomes trial, hip and pelvic fractures were more common on Wegovy in women (1% vs 0.2%) and in people 75 or older (2.4% vs 0.6%).[1]
- Facial volume loss from fast weight loss is not a labeled reaction but is a common concern. See Ozempic face.
Serious side effects and warning signs
Get medical advice promptly for:[1][2]
- Pancreatitis: severe, persistent belly pain that may spread to the back, with or without vomiting. On Wegovy, it was confirmed in 4 people on the drug versus 1 on placebo in the weight-loss trials.[1]
- Gallbladder attack: pain under the right ribs, fever, yellow skin or eyes.
- Dehydration: vomiting or diarrhea that stops you keeping fluids down. Acute kidney injury has been reported, mostly after fluid loss.[1]
- Severe stomach problems: reported in 4.1% on Wegovy injection versus 0.9% on placebo. Semaglutide is not recommended with severe gastroparesis.[1]
- Vision changes: people with diabetic retinopathy can see it worsen. In a 2-year Ozempic trial, retinopathy complications occurred in 3% versus 1.8% on placebo.[2] In June 2025 the European Medicines Agency also concluded that NAION, an optic nerve condition causing sudden vision loss, is a very rare side effect (up to 1 in 10,000 people).[5]
- Low blood sugar: mainly with insulin or a sulfonylurea.[1]
- Thyroid warning: semaglutide caused thyroid C-cell tumors in rodents; whether it does in humans is unknown. Avoid it with a personal or family history of medullary thyroid cancer or MEN 2.[1]
Wegovy’s former warning about suicidal thoughts was removed in 2026 after FDA’s review found no increased risk.[6] Any new low mood still deserves attention.
Tips for managing side effects
- Eat smaller meals and stop when you feel full.
- Go easy on greasy and very sweet foods, especially in the days after your injection.
- Drink fluids steadily to avoid dehydration.[1]
- Tell surgeons and anesthetists that you take semaglutide, because it slows stomach emptying.[1]
- Ask about slowing the dose increase if side effects are hard to manage. If you are moving straight to a higher Wegovy dose, read starting Wegovy at 1.7 mg.
Questions to ask your clinician
- Should I stay on my current dose longer before increasing?
- What can I take for nausea, diarrhea or constipation?
- Do any of my diabetes or blood pressure medicines need adjusting?
- Do I need an eye exam before or during treatment?
- Which symptoms mean I should stop and get help?
This guide is general information. A licensed clinician should set and adjust your dose.
