Guide · Side effects · 3 min read
Constipation and diarrhea
Constipation and diarrhea affect more than 1 in 10 people on Wegovy and Mounjaro, and they are most common when you start and when the dose goes up. 1·2 Constipation is common with weight loss, and it is best dealt with early. 3 Long-lasting constipation can also lead to diarrhea in return. 3
For constipation
- Drink plenty of water and other fluids. 3·4
- Increase fiber gradually. You can add oats, wheat bran or linseed. 3·4
- Prunes and other dried fruit can help. 3
- Walk or run every day. It helps your bowels work more regularly. 4
- Don't put off going to the toilet. Resting your feet on a low stool can make it easier. 4
- Avoid alcohol. 4
You may notice a difference within a few days; sometimes it takes a few weeks. 4
If you use FODMAP mode
Apples and dried fruit are among the high FODMAP foods. 7 Low FODMAP servings for fiber: half a cup of rolled oats (52 g), 2 small green kiwifruit, 1 tablespoon of linseed or 2 tablespoons of chia seeds. 6
For diarrhea
- Drink plenty of fluids; small sips if you feel sick. 5
- Avoid large and fatty meals. 3·5
- Fruit juice and fizzy drinks can make diarrhea worse. 5
- If you have signs of dehydration, your pharmacist can suggest an oral rehydration powder you mix with water. 5
In CalJab
Log constipation and diarrhea in How are you under "More"; the number of days appears in your doctor report. Your fiber target is on Today. Symptom patterns in Premium show whether constipation follows a low-fiber day.
When to see a doctor
- Severe constipation with stomach ache, bloating and vomiting: see a doctor straight away. The Wegovy leaflet lists this as bowel obstruction among serious side effects. 1
- Constipation that is not getting better with treatment, keeps coming back, blood in your poo or tummy pain: see your doctor. 4
- If changes are not enough, your pharmacist can suggest a suitable laxative; laxatives should only be used for a short time. 4
- Diarrhea for more than 7 days, bloody diarrhea or not keeping fluids down: contact a doctor right away. 5
- Don't stop your medicine without talking to your doctor. 1·4
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: Constipation. Last reviewed 26 October 2023. nhs.uk
- 5NHS: Diarrhoea and vomiting. Last reviewed 21 December 2023. nhs.uk
- 6Monash University FODMAP: Getting enough fibre (J. Varney, 2021). monashfodmap.com
- 7Monash University FODMAP: High and low FODMAP foods. monashfodmap.com
Written by the CalJab team, with sources. It does not replace your doctor's advice. Found a mistake? Write to support@caljab.app.