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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Good Cleanse for Weight Loss — UK Prescription Options
If you're looking for a "good cleanse" for weight loss in the UK, prescription weight management medications may be an option worth discussing with your GP. Rather than relying on unproven detox products or fad cleanses, evidence-based medical treatments like GLP-1 injections are available through both NHS specialist services and private prescribing. This guide explains what's actually available, who's eligible, and how to find out if prescription weight loss medication is right for you.
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-Licensed Prescription Weight Loss Medications
The UK has three prescription-only medications licensed specifically for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 and GIP/GLP-1 receptor agonist medications—they work by helping regulate appetite and supporting feeling fuller after smaller meals, alongside a reduced-calorie diet and increased physical activity.
- Mounjaro: Dual GIP and GLP-1 agonist. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy: GLP-1 agonist only. Clinical trials showed average weight loss of approximately 15% of body weight over 68 weeks.
- Saxenda: GLP-1 agonist. Daily injection (not weekly like Mounjaro and Wegovy). Average weight loss of approximately 5–10% of body weight.
All three require a prescription and clinical assessment. Individual results vary significantly. Use our free GLP-1 weight loss calculator above to explore potential weight loss projections at different medication doses, and calculate your BMI to understand where you currently stand on the NHS weight management scale.
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
In the UK, weight loss medication is available through two routes. NHS access: Referral to a tier 3 specialist weight management service (usually through your GP), though availability and waiting times vary significantly by region. Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a GPhC-registered pharmacy—no NHS referral needed.
To find out if you're eligible for prescription weight loss treatment, start by checking your BMI weight loss category 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 (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Your GP can assess your individual situation and discuss options—whether NHS specialist services, private prescribing, or lifestyle-first approaches are right for you.
- 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.
What's the difference between a "cleanse" and actual weight loss medication?
Cleanses and detox products are typically unproven and may not deliver lasting weight loss. Prescription weight loss medications like Mounjaro and Wegovy are licensed, evidence-based treatments that work alongside diet and exercise. They're regulated by the MHRA and have been through clinical trials demonstrating their safety and effectiveness.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may have access at lower BMI thresholds. Speak to your GP about NHS specialist weight management services in your area.
How long does it take to see weight loss results with GLP-1 medication?
Most people begin noticing effects within the first few weeks, though weight loss typically becomes more apparent after 4–8 weeks of treatment. Clinical trials measured results over 12–18 months. Results depend on dose, adherence, diet, and physical activity. Individual results vary significantly.
Is prescription weight loss medication the same as a "cleanse"?
No. Prescription medications work through specific biological mechanisms—GLP-1 agonists activate natural hormone pathways that regulate appetite and blood sugar. They're not cleanses or detoxes; they're prescription-only medicines requiring clinical assessment and ongoing monitoring by a healthcare professional.
Can I get prescription weight loss medication privately if NHS waiting lists are long?
Yes. Private online prescribing services are available in the UK through GPhC-registered pharmacies. You'll have an online consultation with a UK-licensed prescriber, and if clinically appropriate, a prescription will be issued. This route doesn't require an NHS referral and is often faster than NHS specialist services, though it's a private cost.
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.