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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7 Day Detox Weight Loss — Prescription Options in the UK
The concept of a "7 day detox" for gradual weight management is popular, but sustainable weight management in the UK is best supported through lifestyle changes and, where appropriate, prescription medication. If you're looking to lose weight, you may be eligible for prescription weight loss treatment through the NHS or private prescribing. This guide covers your options, eligibility criteria, and how to start a conversation with your GP about weight management support that actually works.
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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.
UK-Licensed Prescription Weight Management Options
If you're interested in weight management UK, three prescription medications are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonist injections that work by helping regulate appetite and supporting you to feel fuller after smaller meals.
- Mounjaro: Once-weekly injection, dual GIP and GLP-1 agonist, doses 2.5mg to 15mg. Clinical trials showed average weight loss of 15–21% body weight when combined with a reduced-calorie diet and increased physical activity.
- Wegovy: Once-weekly injection, GLP-1 agonist only, doses 0.25mg to 2.4mg. Average weight loss in trials was approximately 15% of body weight over 68 weeks.
- Saxenda: Once-daily injection, GLP-1 agonist, doses 0.6mg to 3mg. Can be effective but requires daily administration rather than weekly.
All three are prescription-only medicines requiring clinical assessment before prescribing. Individual results vary significantly, and these medications work alongside, not instead of, dietary and lifestyle changes.
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 and How to Check Your Eligibility
NHS access: Weight loss medication on the NHS is available through specialist tier 3 and tier 4 weight management services. You'll need a referral from your GP, and availability varies considerably by region and ICB (Integrated Care Board). Waiting lists can be lengthy in many areas.
Private access: Prescription weight loss medication is available through private online prescribing services following an online clinical assessment by a UK-licensed prescriber. This is faster than NHS routes but involves a cost, typically £129–£320 per month depending on dose and provider.
Eligibility: Adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea, may be eligible. Your GP can assess whether prescription weight loss medication is right for you and discuss NHS options or refer you for private assessment.
- 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.
Is a 7 day detox actually effective for weight loss?
Short-term detoxes typically cause rapid water loss rather than fat loss, and the weight usually returns quickly. Sustainable weight loss of 0.5–1kg per week, supported by dietary changes and increased physical activity, is recommended by the NHS. If you're struggling to lose weight, speaking to your GP about prescription weight management options may help.
What is GLP-1 weight loss medication and how does it work?
GLP-1 receptor agonist medications like Wegovy and Mounjaro mimic a natural hormone that regulates appetite and blood sugar. They help reduce hunger, support feeling fuller after meals, and slow how quickly food leaves your stomach. They're used alongside a reduced-calorie diet and exercise for best results.
How do I know if I'm eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Your GP can assess your individual circumstances and refer you to a specialist weight management service if appropriate. They can also discuss NHS vs private options.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro is a dual GIP and GLP-1 agonist (may cause slightly greater average weight loss), while Wegovy is GLP-1 only. Clinical trial data showed Mounjaro 15mg resulted in approximately clinically studied weight loss versus Wegovy's approximately 15%. Individual results vary, and either may be suitable depending on your health profile.
Can I use our free tools to track my weight loss journey?
Yes. Use our free BMI calculator to check your starting BMI and track changes over time, our GLP-1 weight loss calculator to explore potential outcomes at different doses if eligible, our weight converter for UK measurements, and our progress tracker to log your weight loss journey month by month.
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.