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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Medical Weight Loss Program Options in the UK
A medical weight loss program in the UK typically involves prescription medication alongside lifestyle changes. If you're struggling with excess weight and have tried diet and exercise alone, you may be eligible for NHS-supported or privately-prescribed weight management treatment. This guide explains your options, how to access them, and what to expect from prescription-based medical weight loss approaches.
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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.
UK-Licensed Prescription Weight Loss Medications
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — once-weekly injection, dual GIP and GLP-1 receptor agonist. Clinical trials showed an average weight loss of 15–21% body weight over 72 weeks when combined with reduced-calorie diet and physical activity.
- Wegovy (semaglutide) — once-weekly GLP-1 injection. Average weight loss in trials was approximately 15% body weight at 68 weeks alongside lifestyle changes.
- Saxenda (liraglutide) — once-daily GLP-1 injection. Average weight loss approximately 8% body weight.
All three are prescription-only and require clinical assessment. You must be eligible based on BMI and health conditions. Individual results vary significantly. These medications work alongside dietary changes and increased physical activity — they are not replacements for lifestyle modifications. A prescriber will assess your suitability based on your personal health circumstances.
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 Routes: How to Access Medical Weight Loss
In the UK, you can access prescription weight loss medication through two routes. NHS route: Referral from your GP to a specialist tier 3 weight management service. This is free but availability varies by region and waiting lists can be lengthy in some areas. Private route: Online consultation with a UK-licensed prescriber, available without NHS referral. You'll need to pass a clinical assessment before a prescription is issued by a GPhC-registered pharmacy. Check your BMI using our free BMI calculator to understand where you stand — adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure, may be eligible. Speak with your GP first — they can advise on local NHS options or support your private route decision.
- 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.
How do I know if I'm eligible for a medical weight loss program in the UK?
You're typically eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds. Use our free BMI calculator to check your personal BMI, then speak with your GP about eligibility.
What's the difference between NHS and private weight loss medication?
NHS access is through specialist services after GP referral — it's free but has regional variation and waiting lists. Private routes use online consultations with UK-licensed prescribers, no referral needed, and prescription is dispensed by pharmacies. Both require clinical assessment; individual results vary. Private treatment typically costs £129–£320 monthly depending on dose.
How much weight can I lose on a medical weight loss program?
Clinical trials showed average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy over several months. However, individual results vary significantly. Weight loss depends on the medication, dose, how long you take it, and adherence to dietary and physical activity changes. Your GP or prescriber can discuss realistic expectations for your situation.
Are prescription weight loss injections safe?
UK-licensed medications like Mounjaro and Wegovy have undergone rigorous safety testing. Common side effects include nausea, diarrhoea, and constipation — these often improve over time. Serious side effects are rare. A prescriber will assess your medical history before prescription. Any concerns should be discussed with your GP or healthcare provider.
Can I use weight loss medication without changing my diet and exercise?
No. UK prescribers require that you combine medication with reduced-calorie diet and increased physical activity for safe, sustainable weight loss. Medication is a tool to support lifestyle changes, not a replacement for them. Track your progress using our free progress tracker to monitor both weight and lifestyle improvements alongside any medication.
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.