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
Detoxifying Water for Weight Loss — What Works in the UK
Detoxifying water is often promoted for weight loss, but evidence for its effectiveness is limited. While staying hydrated is important for health, prescription weight management medications approved in the UK offer more reliable support. If you're looking to lose weight, understanding your options — from lifestyle changes to prescription medication — is essential. Our free BMI calculator can help you assess your starting point, and we've outlined the UK-licensed medication options available to eligible adults below.
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.
UK Prescription Weight Loss Medications — Evidence-Based Options
If you're exploring weight management in the UK, prescription medications offer clinically proven support alongside dietary and lifestyle changes. Three GLP-1 weight loss injections are currently licensed:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist; once-weekly injection; clinical trials showed average weight loss of 15–21% of body weight
- Wegovy (semaglutide) — GLP-1 receptor agonist; once-weekly injection; average weight loss of approximately 15% in trials
- Saxenda (liraglutide) — GLP-1 receptor agonist; daily injection; established option for bmi weight loss support
All three are prescription-only weight loss medication options requiring a clinical assessment. They work by reducing appetite and helping you feel fuller after smaller meals — far more effective than water-based approaches. Our free GLP-1 weight loss calculator can help you estimate potential results at different doses.
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 Started
NHS weight loss medication access: Available through specialist tier 3/4 weight management services (referral from your GP required). Availability and waiting times vary significantly by region. Private access: Available through UK-licensed prescribers following an online clinical assessment — no NHS referral needed.
To find out if you're eligible, check your BMI using our free BMI calculator on this page. Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (type 2 diabetes, hypertension, sleep apnoea), may qualify. Discuss your options with your GP or a licensed prescriber — they'll assess your individual health and recommend the most suitable approach for nhs weight loss or private prescription support.
- 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 detoxifying water actually help you lose weight?
Detoxifying water has no special weight loss properties. Staying hydrated supports metabolism and can help you feel fuller, but water itself doesn't "detoxify" or burn fat. Weight loss requires a calorie deficit. If you're serious about losing weight, prescription medications like Mounjaro or Wegovy offer evidence-based support — far more effective than water alone.
What is the most effective weight loss medication available in the UK?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both UK-licensed and effective. Clinical trials showed Mounjaro produced average weight loss of 15–21%, and Wegovy approximately 15%. Results vary between individuals. A prescriber will assess which is most suitable for you based on your health, medical history, and preferences. Both require prescription and clinical assessment.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. Use our free BMI calculator to check your starting point. For definitive eligibility, speak to your GP (NHS route) or contact a UK-licensed prescriber offering private consultations. Lower BMI thresholds apply to adults of South Asian, Chinese, Black African, or Caribbean heritage.
Can I get weight loss medication on the NHS or do I need to pay privately?
Both options are available in the UK. NHS access is through specialist weight management services (your GP refers you) — but waiting lists can be very long and availability varies by region. Private prescribing is available through online consultations with UK-licensed prescribers; costs typically range from £129–£320 per month depending on dose. Ask your GP about NHS options first, or explore private routes if NHS waiting times are lengthy.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy — meaning someone weighing 100kg might lose 15–21kg on average. However, results vary significantly between individuals. Weight loss is achieved alongside a reduced-calorie diet and increased physical activity. A prescriber will discuss realistic expectations for your situation. Use our GLP-1 weight loss calculator to see projected outcomes at different doses.
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.