Common side effects
| Side effect | Frequency | Notes |
|---|---|---|
| Nausea | ~34% | Most common. Worse during dose increases. Usually improves. |
| Diarrhoea | ~25% | Typically resolves within a few weeks. |
| Vomiting | ~18% | More common at higher doses. |
| Constipation | ~20% | Can persist. Manage with fibre and hydration. |
| Abdominal pain | ~15% | Usually related to eating speed or portion size. |
| Headache | ~12% | Usually resolves early in treatment. |
| Fatigue | ~9% | Typically first few weeks only. |
Ozempic vs Wegovy side effects
Because Ozempic's maximum dose (1mg) is less than half of Wegovy's (2.4mg), most side effects tend to be less intense. However, the types of side effects are identical since both contain semaglutide. Nausea rates are slightly lower (~34% vs ~44%), and vomiting is less common (~18% vs ~24%).
Serious side effects (rare)
- Pancreatitis: Sudden severe abdominal pain radiating to the back. Stop medication and seek emergency care immediately.
- Gallbladder problems: Risk increases with any rapid weight loss. Report upper-right abdominal pain to your doctor.
- Kidney problems: Particularly with dehydration from severe vomiting or diarrhoea. Stay hydrated and report persistent GI symptoms.
- Thyroid concerns: Animal studies showed thyroid C-cell tumour risk. Not confirmed in humans but contraindicated in people with personal or family history of medullary thyroid carcinoma (MTC).
Managing side effects
- Eat smaller, more frequent meals — especially during dose escalation
- Avoid high-fat, greasy, and very rich foods
- Stay well hydrated (at least 2 litres of water daily)
- Eat slowly and stop when you start to feel satisfied (not full)
- Ask your doctor about anti-nausea medication if nausea is persistent
- For constipation: increase fibre, water, and gentle movement
When to contact your doctor
Seek medical attention if you experience severe or persistent vomiting (risk of dehydration and kidney damage), sudden severe abdominal pain (possible pancreatitis), signs of allergic reaction (difficulty breathing, facial swelling), or any symptoms that concern you.