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
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Can Water Aid Weight Loss? Evidence and UK Weight Management Options
Water is often promoted as a weight loss tool, and there is some scientific evidence to support this claim. Drinking adequate water can support appetite control, boost metabolism slightly, and prevent thirst being mistaken for hunger — all of which may help with weight management in the UK. However, water alone is not a weight loss solution. For sustainable weight loss, most people need a combination of reduced-calorie eating, increased physical activity, and sometimes prescription medication. This guide covers what the evidence says about water and weight loss, plus the prescription weight management options available to eligible UK adults.
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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.
How Water Supports Weight Management
Research suggests that drinking water does have a modest role in weight management. Drinking water before meals may help reduce overall calorie intake by creating a feeling of fullness, which can lead to eating smaller portions. Studies have shown that people who drink water regularly tend to consume fewer calories from sugary drinks and snacks — a significant factor in weight loss uk outcomes.
- Metabolism boost: Drinking cold water may increase calorie burn slightly as your body works to warm it, though this effect is minimal
- Appetite suppression: Water fills the stomach temporarily, which can reduce hunger signals to the brain
- Hydration and energy: Proper hydration supports physical activity performance, making exercise easier to sustain
However, the NHS emphasises that water is a supportive tool only — sustainable weight loss requires a calorie deficit through diet and activity. For most people, drinking 6–8 glasses (1.2–1.6 litres) of water daily is recommended. You can use our free progress tracker to log your daily habits, including water intake and weight changes, to see what works for your individual situation.
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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.
Prescription Weight Loss Options for UK Adults
If you're struggling with weight management through diet and exercise alone, prescription weight loss medications are available in the UK for eligible adults. These include Mounjaro (tirzepatide), a dual GLP-1 and GIP receptor agonist, and Wegovy (semaglutide), a GLP-1 receptor agonist. Both are prescription-only medicines approved by the MHRA for weight loss uk in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure.
Clinical trials have shown that these medications, used alongside reduced-calorie diets and increased physical activity, support an average weight loss of 15–21% of body weight. Access is available through NHS specialist weight management services or private prescribing following a clinical assessment. Our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses, whilst our BMI calculator determines whether you might be eligible based on your current measurements.
- 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.
Does drinking water actually help with weight loss?
Water can support weight loss modestly by reducing hunger, increasing satiety before meals, and replacing sugary drinks — but it is not a weight loss solution on its own. The NHS recommends water as part of a broader approach that includes a calorie-controlled diet and regular physical activity. For significant weight loss, most people need additional support.
How much water should I drink daily for weight management?
The NHS recommends 6–8 glasses (1.2–1.6 litres) of water daily for general health. Drinking water before meals may help reduce calorie intake, but individual needs vary based on activity level, climate, and personal health. Your GP can provide personalised hydration guidance.
What prescription weight loss medications are available on the NHS in the UK?
Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide) are NHS-licensed for weight management. Access is through specialist tier 3 weight management services, usually via GP referral. Eligibility is based on BMI and weight-related health conditions. Availability varies significantly by region.
What is the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist; Wegovy is a GLP-1 receptor agonist only. Clinical trials showed Mounjaro supported average weight loss of 15–21%, whilst Wegovy supported approximately 15%. Both are once-weekly injections. A prescriber will assess which is more suitable for your individual circumstances.
How do I find out if I'm eligible for prescription weight loss medication?
Speak to your GP, who can assess your BMI, health history, and weight-related conditions. If eligible, you may be referred to an NHS specialist weight management service (availability varies by region) or you can explore private prescribing through a UK-licensed prescriber following an online clinical assessment. Use our free BMI calculator to check your current BMI category.
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.