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
Does Water Help in Weight Loss?
Yes, drinking water can support weight loss as part of an overall healthy lifestyle. Water helps you feel fuller, boosts metabolism slightly, and reduces the chance of mistaking thirst for hunger. However, water alone won't lead to significant weight loss—sustainable results require a calorie deficit through diet and physical activity. For adults struggling with excess weight, NHS weight management services and prescription options like GLP-1 injections may also be available. Understanding how hydration fits into your broader weight management strategy is key to success.
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.
Prescription Weight Management Options in the UK
If you're looking to lose weight and have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), you may be eligible for prescription weight loss medication. The UK has three licensed options:
- Mounjaro (tirzepatide) — a once-weekly injection that acts as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and reduce food cravings
- Wegovy (semaglutide) — a once-weekly GLP-1 injection that signals fullness to the brain
- Saxenda (liraglutide) — a daily GLP-1 injection for longer-term weight management
In clinical trials, these medications helped participants lose an average of 14–21% of body weight when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly. All are prescription-only and require a clinical assessment before use.
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 — How to Get Help
NHS route: Referral to a tier 3 specialist weight management service through your GP. Eligibility and waiting times vary by region (ICB). Many areas have significant waiting lists.
Private route: Online consultation with a UK-licensed prescriber, followed by prescription and dispensing through a GPhC-registered pharmacy. Available without NHS referral and typically faster access.
Your first step is a conversation with your GP about your weight and health goals. They can assess your eligibility, discuss what lifestyle changes and support are available, and refer you to specialist services if appropriate. Use our free BMI calculator above to check your current BMI before your appointment—this helps inform the conversation.
- 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 more water actually help you lose weight?
Water itself has no calories, and staying hydrated can help you feel fuller and avoid mistaking thirst for hunger. Some research suggests drinking water slightly increases metabolic rate. However, water alone won't create the calorie deficit needed for weight loss. You need to combine hydration with a balanced diet and physical activity for meaningful results.
How much water should I drink daily for weight loss?
The NHS recommends around 6–8 glasses of fluid daily (about 1.5 litres), though individual needs vary based on activity level and climate. Drinking water instead of sugary drinks helps reduce calorie intake. There's no clinically supported amount—consistent hydration combined with healthy eating and exercise is what matters.
What prescription weight loss options are available on the NHS?
Through NHS specialist weight management services, you may be eligible for Mounjaro, Wegovy, or Saxenda if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Access requires GP referral and varies by region. Private options are also available through licensed UK prescribers.
Can I get weight loss injections privately if I'm not eligible for NHS?
Yes. Private weight loss injections (Mounjaro and Wegovy) are available through online consultations with UK-licensed prescribers and dispensed by GPhC-registered pharmacies. A clinical assessment is still required. Costs typically range from £129–£320+ per month depending on dose and provider.
How does prescription medication work alongside diet and water intake?
Medications like Mounjaro and Wegovy work by reducing appetite and helping you feel fuller—they support, not replace, healthy eating. Drinking water, eating a balanced reduced-calorie diet, and staying active all work together. Try our free GLP-1 weight loss calculator above to estimate potential results with medication alongside lifestyle changes.
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.