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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What's the Difference Between Mounjaro and Wegovy in the UK?
Mounjaro and Wegovy are both prescription-only weight management injections available in the UK, but they work differently and cost different amounts. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates only the GLP-1 pathway. Both are given as once-weekly injections, but the key differences lie in their mechanism, dosing schedule, and UK pricing. Understanding these distinctions helps you and your GP or prescriber make an informed choice about which medication may be appropriate for your circumstances.
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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.
Mounjaro vs Wegovy: Cost and Access in the UK
Mounjaro (tirzepatide) typically costs between £140 and £250 per month privately in the UK, depending on your dose (starting at 2.5 mg, escalating to a maximum of 15 mg weekly). Wegovy (semaglutide) generally costs between £129 and £210 per month, starting at 0.25 mg and reaching a maximum of 2.4 mg weekly. In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, while Wegovy showed approximately 15% average weight loss — though individual results vary significantly. Both medications are available through private online prescription services following a clinical assessment by a UK-licensed prescriber. The cost difference is modest, but the underlying medication mechanism differs: Mounjaro's dual-action GIP/GLP-1 approach may offer slightly greater average weight loss, while Wegovy is an established, well-researched single GLP-1 medication. Neither is currently widely available on the NHS outside specialist tier 3 or 4 weight management services, which have limited capacity and long waiting lists in most regions.
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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 Mounjaro or Wegovy
NHS route: Request a referral from your GP to a specialist tier 3 weight management service. NICE has approved both tirzepatide (Mounjaro) and semaglutide (Wegovy) for use within NHS specialist services, but regional ICBs vary in availability. Waiting lists can extend many months or years. Private route: Use an online consultation with a UK-licensed prescriber. You'll complete a health questionnaire, discuss your medical history and suitability, and receive a prescription if approved. The prescription is dispensed by a GPhC-registered pharmacy. Private access typically takes days rather than months. Both routes require a clinical assessment — no medication is dispensed without one. Try our free GLP-1 weight loss calculator to understand potential outcomes at different doses, and use our BMI calculator to establish your baseline health status before any consultation.
- 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.
Which is cheaper in the UK — Mounjaro or Wegovy?
Wegovy is typically slightly cheaper (around £129–£210/month) compared to Mounjaro (£140–£250/month), but costs vary by dose and provider. Both are more expensive than NHS prescriptions if available through the NHS, but private costs are comparable. Individual pricing depends on the dose you're prescribed and the specific pharmacy or service provider.
Is Mounjaro available on the NHS in the UK?
Mounjaro is approved by NICE for NHS use within specialist tier 3 and 4 weight management services, but availability is very limited and varies significantly by region. Most people access it privately. If you meet NHS eligibility criteria (BMI 30+ or 27+ with weight-related conditions), ask your GP for a referral to your local specialist weight management service to understand current waiting times.
How much weight loss can I expect from Mounjaro vs Wegovy?
Clinical trials showed Mounjaro helped participants lose an average of 15–21% of body weight, while Wegovy showed approximately 15% average loss. However, individual results vary significantly based on diet, exercise, dose, and personal factors. Results are achieved alongside a reduced-calorie diet and increased physical activity — not from the medication alone.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official established conversion chart, though approximate equivalences exist (e.g., Mounjaro 10 mg is roughly equivalent to Wegovy 1.7 mg). Any switch requires a new clinical assessment and prescription. Your prescriber will advise on the safest transition approach.
What's the difference between Mounjaro and tirzepatide?
Mounjaro is the brand name for tirzepatide. They are the same medication — tirzepatide is the active ingredient, and Mounjaro is how it's marketed in the UK. Similarly, Wegovy is the brand name for semaglutide. When you receive a private prescription, you may see either the brand name (Mounjaro) or the generic ingredient name (tirzepatide) listed on your prescription.
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