Guide · Side effects · 3 min read
Nausea and vomiting
Nausea is the most common digestive side effect of GLP-1 medicines: with Wegovy and Mounjaro it affects more than 1 in 10 people. 1·2·3 It is most common when you start treatment and after a dose increase, and for most people it eases over time. 1·2·3 It often comes in the morning or after a long time without eating. 3
Going hungry can make it worse
Not eating because of nausea can make nausea worse, which makes eating even harder. 3 To break the cycle, small but regular meals are advised: a small breakfast, then a small meal every 3 to 4 hours, with enough fluids. 3
What may help
- Skip large meals. Vomiting is more likely after a large meal. 3
- Eat slowly. Don't have a large drink with your meal. 6
- Go easy on fried and fatty food. In the first days, on high-fiber foods too. 3·6
- Take regular sips of a cold drink. Ginger or peppermint tea helps some people too. 3·6
- Don't lie down soon after eating. Clothes that are tight around your waist can make it worse too. 6
- Avoid cooking strong-smelling food. Fresh air can help. 6
- Stay away from alcohol. It can make nausea, vomiting and reflux worse. 3·4·5
If you are sick
Vomiting and diarrhea can make you lose fluids, which can affect your kidneys. 1·2 Start with small sips, then slowly drink more. 8 Caffeinated drinks and alcohol make fluid loss worse. 8 If you have lost a lot of fluid, your pharmacist can suggest an oral rehydration solution, a powder you mix with water and drink. 8 Eat when you feel able to. 7
Signs you may be dehydrated: feeling thirsty, dark yellow pee, peeing less often than usual, feeling dizzy, feeling tired and a dry mouth. 8
In CalJab
When you log nausea in How are you, that day becomes a gentle day: Today speaks to you gently, sip reminders come, recipes that are easy on the stomach come first in Recipes, and you can switch the rest of your plan to gentle recipes. The symptom map shows which dose days nausea rises; it also appears in your doctor report.
When to see a doctor
- If nausea doesn't ease in a few days, keeps coming back or is hard to cope with, talk to your doctor or pharmacist. They can prescribe medicine for nausea if needed. 4·5·6
- Don't stop your medicine without talking to your doctor. 1·4
- If you can't keep fluids down, feel dizzy when you stand up and it doesn't pass, or pee much less than usual, reach a doctor the same day. 7·8
- Severe stomach pain that does not go away and may spread to your back: see a doctor straight away. It can be a sign of an inflamed pancreas. 1·2·4
- Severe constipation with stomach ache, bloating and vomiting: see a doctor. The Wegovy leaflet lists this as bowel obstruction among serious side effects. 1
- Vomit with blood, vomit that looks like coffee grounds or green vomit, trouble breathing, or swelling of the lips, tongue or throat: get emergency help. 2·4·7
Make decisions about your medicine and dose with your doctor.
Sources
- 1Wegovy product information and package leaflet. European Medicines Agency (EMA). Accessed 20 October 2026. ema.europa.eu
- 2Mounjaro product information and package leaflet. European Medicines Agency (EMA). Accessed 20 October 2026. ema.europa.eu
- 3Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from ACLM, ASN, OMA and The Obesity Society. Obesity 2025;33(8):1475-1503. pmc.ncbi.nlm.nih.gov
- 4NHS: Semaglutide. Last reviewed 15 May 2026. nhs.uk
- 5NHS: Tirzepatide. Last reviewed 15 May 2026. nhs.uk
- 6NHS: Feeling sick (nausea). Last reviewed 17 November 2023. nhs.uk
- 7NHS: Diarrhoea and vomiting. Last reviewed 21 December 2023. nhs.uk
- 8NHS: Dehydration. Last reviewed 1 May 2026. nhs.uk
Written by the CalJab team, with sources. It does not replace your doctor's advice. Found a mistake? Write to support@caljab.app.