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 Does Drinking Water Help With Weight Loss?
Drinking water supports weight loss by increasing satiety, boosting metabolism, and reducing calorie intake — but it works best alongside other lifestyle changes. For many UK adults, combining adequate hydration with dietary changes and physical activity is effective. However, if you're struggling with weight management despite these efforts, prescription weight loss medications are now available through the NHS and private prescribing for eligible adults. Our free GLP-1 weight loss calculator can help you understand your options, and a conversation with your GP is the first step to exploring whether prescription support might be right for you.
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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.
Water, Weight Loss, and Prescription Medication in the UK
Water itself doesn't directly cause weight loss, but adequate hydration supports the mechanisms that do. Drinking water before meals can increase feelings of fullness, potentially reducing overall calorie intake. It also helps your body metabolise fat more efficiently and reduces the likelihood of confusing thirst with hunger — a common barrier to successful weight management in the UK.
For eligible UK adults, prescription weight loss injections work alongside hydration and diet to enhance results. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that helps regulate appetite and reduce food cravings. Wegovy (semaglutide) is a GLP-1 agonist with similar effects. In clinical trials, participants on these medications lost an average of 15–21% of their body weight when combined with lifestyle changes like improved hydration and reduced-calorie diets. Saxenda (liraglutide) is also available as a daily injection option. All are prescription-only and require a clinical assessment from a licensed prescriber.
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.
NHS vs Private Access: Finding the Right Weight Loss Path for You
In the UK, prescription weight loss medication is available through two routes: NHS specialist services and private online prescribing. NHS access is typically through tier 3 weight management services following a GP referral, though availability and waiting times vary significantly by region. Private prescribing is faster and doesn't require an NHS referral — you can access a UK-licensed prescriber via GPhC-registered online pharmacies following a brief online assessment.
Eligibility for prescription weight loss medication in the UK generally requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. People of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to higher health risks at those levels. Your GP or a licensed prescriber will assess whether you're eligible and whether medication is appropriate for your individual circumstances.
- 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 alone cause weight loss?
No — water supports weight loss mechanisms but doesn't directly cause it. Hydration reduces hunger signals, improves metabolism, and helps prevent calorie-dense drink consumption. Sustainable weight loss requires a calorie deficit, usually achieved through dietary changes, physical activity, and adequate hydration working together.
How much water should I drink daily for weight loss?
The NHS recommends approximately 6–8 glasses (1.5–2 litres) of fluid daily for most UK adults. Drinking water before meals can increase satiety. However, no specific amount "assures" weight loss — individual needs vary by activity level, climate, and health status. Your GP can advise on your personal hydration needs.
Can prescription weight loss injections like Mounjaro replace diet and exercise?
No. Mounjaro, Wegovy, and Saxenda are designed to work alongside lifestyle changes, not replace them. They help regulate appetite and support adherence to reduced-calorie diets and physical activity — but diet, exercise, and hydration remain essential for sustainable weight loss and long-term health.
How do I know if I'm eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related conditions like diabetes or hypertension. However, availability varies by region. Speak with your GP about specialist weight management services in your area, or use our free BMI calculator to check where you fall on the NHS weight categories.
What's the difference between Mounjaro and Wegovy?
Both are prescription-only once-weekly injections for weight management in UK adults. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trial data suggests similar average weight loss outcomes (around 15–21% body weight), though individual results vary. Your prescriber will advise which is more appropriate for you.
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.