Staying hydrated on weight loss injections

Staying hydrated is a crucial component of a healthy diet. This is true whether or not you're using weight loss injections like Wegovy or Mounjaro.

However, it's worth paying special attention to your fluid intake when using weight loss injections. Dehydration is bad for your overall health and can make it harder to manage the side effects of Wegovy and Mounjaro.

In this guide, we cover the key facts about hydration on weight loss injections, how to spot signs of dehydration and tips for staying hydrated.

Key points you need to know

• Staying hydrated is vital for nutrition and overall health.
  
  
• Hydration is especially important when taking weight loss injections. Being dehydrated can make certain side effects, such as nausea and constipation, worse.
  
  
• Weight loss injections can make it harder to remember to stay hydrated. Along with reducing appetite, they can reduce thirst. However, even if you don't feel thirsty, you should still make sure to drink enough fluids throughout the day.
  
  
• You may find it uncomfortable to drink the recommended fluid intake at first. That's because Wegovy and Mounjaro slow stomach emptying and make you feel full more quickly. However, this discomfort should pass as you adjust to the medication.
  
  

How much water should I drink on weight loss injections?

The UK government's Eatwell Guide recommends drinking six to eight glasses of fluids per day. This is just an average. You may need to drink more in certain cases, such as on hot days, when you're physically active or if you're unwell.¹

For good health and nutrition, aim to drink water, low-fat milk or sugar-free drinks.¹

These guidelines also apply to people taking weight loss injections. You don't usually need to change your fluid intake while using Wegovy or Mounjaro.

However, diarrhoea and vomiting can lead to rapid dehydration. If you experience these side effects, it's important to drink regularly to replace these lost fluids.

How can I tell if I'm dehydrated on weight loss injections?

Wegovy and Mounjaro can dull thirst and make it harder to track fluid intake. However, if you notice any of these signs, it's a clue that you may need to drink more fluids.

• Urine colour: lots of things can affect the colour of urine (pee), including certain foods and medications.² However, darker urine can also be a sign of dehydration.
• Dryness: a dry mouth, dry skin or cracked lips can be signs that you need to increase your fluid intake.
• Tiredness and dizziness: feeling tired, dizzy or weak can signal dehydration.
• Headaches: if you have a persistent headache, dehydration could be the cause.
• Rapid heart rate: dehydration can make the heart pump faster to supply oxygen to the body.
  
  

Tips for staying hydrated on weight loss injections

Remember: on Wegovy or Mounjaro, hydration is your friend. It can help you manage side effects, replace lost fluids and adjust to the medication, as well as benefit overall health.

If you find it hard to get enough fluids, try these tips:

• Set reminders: use alarms on your phone or dedicated hydration apps to schedule regular water breaks.
• Carry a water bottle: keep a bottle with you as you work or go about your day. That way, it's easy to remember to take a sip now and then.
• Drink little and often: it's much easier to drink small amounts frequently than gulping a full glass all at once – especially when you feel full.
• Try flavoured water: water is good for you, but some people don't like the taste. If that's you, try adding natural flavourings like lemon, mint or cucumber.
• Don't forget foods: your food intake can help with hydration, too. Try incorporating water-rich foods, such as cucumber and soups, into your daily diet.
  
  

Founded by UK obesity specialists, Semapen offers guided online programmes to help people lose weight and learn healthy habits. Our treatments include expert-led Wegovy and Mounjaro programmes, as well as the drug-free SemaHealth meal replacement programme. Why not take our quick online consultation to find out if you're eligible?

Sources

1. NHS (2023) Water, drinks and hydration. Retrieved from https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/water-drinks-nutrition/

2. East London Health & Care Partnership (n.d.) All you need to know about Urine! [leaflet]. Retrieved from https://northeastlondon.icb.nhs.uk/wp-content/uploads/2022/04/MM-ELHCP_All_about_Urine_leaflet.pdf

This article was reviewed and approved by Lujain Alhassan, Bariatric Nutritionist, on 11 April 2026.