The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
How Much Water Should You Drink A Day On Mounjaro?
Staying hydrated is important when taking Mounjaro (tirzepatide), especially as nausea and digestive changes are common side effects. While there's no single "correct" amount, most healthcare professionals recommend aiming for 6–8 glasses (1.5–2 litres) of water daily on Mounjaro. However, individual needs vary based on activity level, climate, and how your body responds to the medication. This guide explains hydration on Mounjaro and when to seek advice from your GP or prescriber.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Hydration Guidance While Taking Mounjaro
General hydration recommendations for adults on Mounjaro suggest drinking approximately 1.5–2 litres of water daily (roughly 6–8 glasses). This baseline supports your body's natural functions and helps manage common Mounjaro side effects including nausea and constipation. Because Mounjaro slows gastric emptying and can cause digestive symptoms, adequate hydration is especially important — dehydration can worsen nausea and reduce how well the medication works.
- Drink water consistently throughout the day rather than large amounts at once
- Sip slowly, especially if you're experiencing nausea — large gulps may trigger symptoms
- Avoid carbonated drinks initially if they worsen bloating or stomach discomfort
- Monitor your urine colour — pale urine suggests adequate hydration; dark urine suggests you need more water
- Increase intake during hot weather or if you exercise regularly
If you're taking other medications alongside Mounjaro or have kidney or heart conditions, discuss your specific hydration needs with your GP or prescriber, as they may recommend adjusted intake.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Hydration, Nausea, and When to Seek Help
Nausea is one of the most frequently reported side effects of Mounjaro, and staying hydrated can help reduce its severity. Sipping water throughout the day — rather than drinking large volumes at once — often helps manage nausea more effectively. If you find yourself unable to keep fluids down due to severe nausea or vomiting, contact your prescriber or GP immediately, as persistent dehydration can become serious.
- Nausea typically improves within 2–4 weeks as your body adjusts to Mounjaro
- Ginger tea or electrolyte drinks (in moderation) may help some people, but water remains the primary choice
- If nausea prevents you from staying hydrated, your prescriber may discuss dose adjustment or anti-nausea strategies
Use our GLP-1 weight loss calculator to understand what to expect when starting Mounjaro, and track your hydration and symptom changes with our free progress tracker as you adjust to the medication.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How much water should I drink daily on Mounjaro?
Aim for 1.5–2 litres (6–8 glasses) daily. Drink consistently throughout the day rather than all at once. Individual needs vary by activity level, climate, and body response. If you have kidney or heart conditions, discuss with your GP.
Will Mounjaro make me more or less thirsty?
Mounjaro may reduce appetite signals, which can sometimes include reduced thirst perception. Monitor your fluid intake intentionally and drink water on a schedule rather than waiting until you feel thirsty. Constipation and nausea are common side effects, and staying hydrated helps manage both.
Can I drink other fluids instead of water on Mounjaro?
Water is ideal. Limit caffeine and sugary drinks as they may worsen nausea. Herbal tea, diluted fruit juice, and electrolyte drinks are acceptable in moderation. Avoid carbonated beverages initially if they trigger bloating or stomach discomfort.
What if I feel too nauseous to drink water on Mounjaro?
Sip small amounts slowly rather than drinking large quantities at once. Try room-temperature or slightly warm water. If severe nausea prevents you from staying hydrated or persists beyond 4 weeks, contact your prescriber — dose adjustment or anti-nausea support may help.
Is hydration different on Mounjaro compared to Wegovy?
Both Mounjaro and Wegovy (semaglutide) are GLP-1-based medications with similar hydration recommendations: 1.5–2 litres daily. Mounjaro is a dual GIP/GLP-1 agonist, which may cause slightly different symptom patterns, so listen to your body and discuss any concerns with your prescriber.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.