Guide · Starting · 3 min read
Fluids and electrolytes
The nausea, vomiting and diarrhea that can come with GLP-1 medicines can make you lose fluids, which can affect your kidneys. 1·2·3 So drinking enough matters, especially if you have kidney problems. 1·2
How much
For most people the guide is pee that is a clear pale yellow. 4 The UK Eatwell Guide suggests 6 to 8 cups or glasses of fluid a day, but this is only a guide. 4 You may need more in a hot environment, when you are active for long periods, or when you are unwell. 4
What counts
- Water is a healthy and cheap choice. 4
- Lower-fat milk, lower-sugar drinks, tea and coffee all count too. 4
- Food gives fluid as well, for example soup and fruit such as melon. 4·5
- Keep fruit juice and smoothies to one small glass (150 ml) a day, with a meal. 4
- Have caffeine in moderation. 4
If drinking feels hard
- Drink regularly through the day. 4
- Don't have a large drink with a meal. When you feel sick, small sips of a cold drink can be easier. 6
- If you don't like the taste of water, try sparkling water, no added sugar squash or a slice of lemon. 4
If you are sick or have diarrhea
- Start with small sips, then slowly drink more. 5
- Lost salts and minerals need replacing too; your pharmacist can suggest an oral rehydration solution, a powder you mix with water. 5
- Fruit juice and fizzy drinks can make diarrhea worse. 7
- Caffeinated drinks and alcohol make fluid loss worse. 5
Signs of dehydration
Feeling thirsty, a headache, dark yellow and strong-smelling pee, peeing less than usual, feeling dizzy, feeling tired and a dry mouth. 5 If you feel dizzy when you stand up and it does not pass, pee much less than normal or feel unusually tired, contact a doctor right away. 5
In CalJab
The glasses on Today show your water for the day; your water target is in Your targets. On a gentle day a sip reminder comes every two hours.
Ask your doctor any questions about your medicine and your health.
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: Water, drinks and hydration. Last reviewed 17 May 2023. nhs.uk
- 5NHS: Dehydration. Last reviewed 1 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
Written by the CalJab team, with sources. It does not replace your doctor's advice. Found a mistake? Write to support@caljab.app.