Understanding Hydration on GLP-1s: Why You Need to Drink Enough Water

Did you know around 60% of the human body is made up of water? It is a vital nutrient that plays a key role in many of our body’s functions. Including regulating body temperature, eliminating waste and aiding digestion – just to name a few.

To keep everything running smoothly, we need to keep our fluid levels topped up. That’s always important. But when you’re on GLP-1 medication, your body undergoes changes such as reduced thirst and appetite, making drinking enough fluids even more crucial. 

Staying well hydrated is an essential part of nutrition. It can help ease common side effects, boost your energy levels and support digestion as you lose weight.

Why Do I Need to Stay Hydrated?

Staying hydrated is important because it supports your whole body. It helps:

• Regulate body temperature 
• Move nutrients and oxygen through the bloodstream 
• Support digestion and preventing constipation 
• Remove waste products through the kidneys 
• Keep joints lubricated to help us move 
• Protect organs and tissues

Why Is Hydration Important on GLP-1 Medication?

Staying hydrated while taking GLP-1 weight medication isn’t just about quenching thirst – it can help you feel much better throughout your journey. These medications often dull your thirst response and reduce your appetite, making it easy to drink too little without realising. 

Even mild dehydration can make side effects like nausea, fatigue, dizziness, and constipation worse. 

Sipping fluids throughout the day and including water-rich foods, like soups, fruits, and vegetables, can make a big difference in how you feel. 

What Happens When You’re Dehydrated?

Dehydration happens when your body loses more water than it takes in. 

This can happen more easily if you’ve been exercising, sweating, experiencing vomiting or diarrhoea, or simply forgetting to drink enough. 

Common signs of dehydration include: 

• Headaches 
• Dizziness or light-headedness 
• Dry mouth or lips 
• Dark yellow urine or reduced urine output 
• Fatigue or low energy 
• Constipation 

Will Drinking Water Help With Weight Loss on GLP-1s?

While drinking water alone won’t lead to weight loss without changes in diet or activity, it can still support your goals in many meaningful ways. For example: 

• Drinking water before meals may help you feel fuller, leading to smaller portions

• Replacing sugary drinks with water can reduce your calorie and sugar intake

• Staying hydrated helps support digestion and energy levels – both important when trying to be more active

Although the research is mixed on whether water alone causes weight loss, it’s clear that hydration plays an important supporting role in any healthy lifestyle. 

How Much Water Do I Need?

Everyone’s hydration needs are different. Factors like age, body size, how much you exercise, and the temperature outside can all make a difference. 

However, according to Public Health England, a good general guide is to: 

• Drink around 6–8 glasses of fluid per day

• Aim for clear pale yellow urine as a sign of good hydration

Don’t wait until you feel thirsty to drink. Thirst is often a sign that you’re already mildly dehydrated. 

What Should I Drink?

While plain water is the best choice for most people, variety can help you stay on track. Here are some good options that count towards your intake:

• Water (still or sparkling)
• Green or herbal teas 
• Diluted sugar-free squash 
• Milk and milk alternatives
• Sugar-free soft drinks in moderation 
• Caffeinated drinks in moderation

Caffeine can act as a mild diuretic, which means it may increase how often you urinate. This doesn’t necessarily lead to dehydration. But it’s still a good idea to balance these with non-caffeinated drinks and not rely on them as your main source of fluids.

Foods, like soup and broths and water-rich fruit and vegetables, also count towards hydration.

Be careful with:

• Fizzy Drinks (Regular or Diet). These can count toward hydration. But they may cause bloating or discomfort, especially on GLP-1s.

• Alcohol. Alcohol can increase side effects and may reduce the overall effectiveness of GLP-1 medications. It’s not recommended as a regular source of fluids. GLP-1s can also heighten the effects of alcohol on your body, meaning you may become intoxicated more quickly than usual. Always follow your healthcare provider’s advice when it comes to alcohol use. We recommend you avoid drinking alcohol on Mounjaro.

5 Hydration Tips to Stay on Track

Keeping up your fluid intake can be easier than you think. Try these 5 simple tips: 

1. Invest in a Large Water Bottle with Markings. Bottles that show how much you’ve drunk by time of day can help you stay consistent and on track.

2. Set Gentle Reminders. Use apps on your phone to nudge you to drink regularly.

3. Eat Your Water! Include hydrating foods like cucumbers, watermelon, oranges, and soups.

4. Flavour Your Water. Add fresh lemon, mint, or berries for variety without sugar.

5. Use an Electrolyte Drink Occasionally. Drink it when you’re unwell, sweating more, or experiencing vomiting or diarrhoea. 

Key Takeaways

• Hydration supports your whole body. Water helps with digestion, energy, waste removal, and more – your body truly can’t function well without it.

• GLP-1 medications reduce thirst. Even if you don’t feel thirsty, you still need fluids – especially if you’re feeling tired, dizzy, or nauseous.

• Water can support weight loss. It may help reduce appetite, replace high-calorie drinks, and support energy for activity.

• Dehydration makes side effects worse. Headaches, nausea, fatigue, and constipation can all be made worse by not drinking enough.

• Simple strategies make a big difference. Bottles with markings, hydration reminders, and water-rich foods can all help you stay topped up daily.

References

Public Health England, 2016. The Eatwell Guide [PDF]. Available at: GOV.UK website: https://assets.publishing.service.gov.uk/media/5bbb790de5274a22415d7fee/Eatwell_guide_colour_edition.pdf (Accessed: 24 June 2025)

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