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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Weight Loss Stories: UK Prescription Medication Guide
Weight loss stories often highlight the importance of finding the right approach for your individual circumstances. In the UK, prescription weight management medication has become increasingly accessible alongside lifestyle changes, offering eligible adults new options alongside traditional diet and exercise. This guide explores the prescription weight loss medications available in the UK, who can access them, and how they fit into a complete weight management plan.
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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 Weight Loss Medications Explained
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical evidence showed average weight loss of approximately 15% of body weight at the maximum dose.
- Saxenda (liraglutide) — a daily GLP-1 injection. A longer-established option with proven efficacy.
All three are prescription-only and require a clinical assessment. Eligibility depends on your BMI and health circumstances. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses, though individual results vary significantly.
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.
Accessing Weight Loss Medication: NHS vs Private
NHS access: Specialist tier 3 weight management services can prescribe these medications, though availability varies significantly by region and waiting lists can be lengthy. Your GP can refer you, but you'll need a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes, hypertension, or sleep apnoea) to be considered.
Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber — no NHS referral needed. This route is typically faster but involves upfront costs. Whichever route suits you, calculating your current BMI using our free BMI calculator is a helpful first step in understanding your eligibility and starting a conversation with your GP about weight management options.
- 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 makes UK weight loss prescription medication different from other countries?
The UK has NICE-approved medications specifically licensed for weight management, and access is guided by NHS guidelines. Medications are prescribed through specialist services or private prescribers following clinical assessment. The BMI thresholds and eligibility criteria are tailored to UK health data and population risk profiles.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary considerably. Weight loss depends on your starting weight, adherence to the medication regimen, and lifestyle changes. Some people lose more, others less. Your prescriber can discuss realistic expectations based on your specific circumstances.
Are these weight loss injections assured to work?
No medication assures weight loss. These injections work best when combined with a reduced-calorie diet and increased physical activity. They may help reduce appetite and support feeling fuller, but they're not a replacement for lifestyle changes. Success depends on individual biology, consistency, and commitment to overall health changes.
Can I get weight loss medication on the NHS if I'm overweight but not obese?
Yes, potentially. If your BMI is 27–29.9 and you have a weight-related health condition (type 2 diabetes, prediabetes, hypertension, sleep apnoea, or cardiovascular disease), you may be eligible through NHS specialist services. Your GP can assess whether you meet local criteria for specialist referral.
What should I do if I think prescription weight loss medication might help me?
Start by speaking to your GP about your weight management goals. They can discuss whether you're eligible, explain NHS specialist service options in your area, or suggest private prescribing routes. Use our BMI calculator to understand your current BMI category first — it's helpful context for that conversation.
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.