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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Is Mounjaro or Wegovy Better in the UK?
Choosing between Mounjaro and Wegovy depends on cost, access, and how your body responds to each medication. Both are prescription-only GLP-1 or dual-action weight loss injections available in the UK, but they differ significantly in price, availability through the NHS, and how they work. This guide compares both options to help you understand which might suit your situation better, whether you're accessing treatment privately or through the NHS.
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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) is a dual GIP and GLP-1 receptor agonist available through NHS specialist weight management services or private prescription. Private costs typically range from £129–£320 per month depending on your dose, with the KwikPen containing 4 weekly injections. Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg weekly.
Wegovy (semaglutide) is a GLP-1-only receptor agonist, also available via NHS or private routes. Private Wegovy costs are comparable—approximately £129–£300 monthly—though pricing varies by provider and dose. Wegovy starts at 0.25 mg and reaches a maximum of 2.4 mg weekly.
In clinical trials, Mounjaro demonstrated slightly higher average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight). However, individual results vary considerably, and the "better" option depends on your eligibility, health profile, and response to treatment. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses for either medication.
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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: Which Route Is Right for You?
NHS access is free but limited by regional availability and specialist referral requirements. You'll typically need a GP referral to a tier 3 weight management service, and waiting lists can extend months or years depending on your NHS ICB (integrated care board). NICE has approved both tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use, but access varies significantly across England, Scotland, Wales, and Northern Ireland.
Private access is faster and doesn't require NHS referral. You complete an online consultation with a UK-licensed prescriber who assesses your eligibility based on BMI and health conditions. If approved, your prescription is dispensed by a GPhC-registered pharmacy. Private treatment begins within days rather than months. Calculate your BMI using our free tool to check your eligibility threshold before consulting a prescriber.
The online consultation process is straightforward: you'll complete a medical questionnaire covering your weight, height, medical history, and current medications. The prescriber reviews this and contacts you if they need clarification. If you're suitable for treatment, a prescription is issued and your medication dispatched. Costs accumulate over time—a year of Mounjaro at 15 mg weekly costs approximately £1,500–£3,800 privately, whilst Wegovy at 2.4 mg costs roughly £1,500–£3,600 annually, depending on your pharmacy and exact dose.
- 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 Mounjaro or Wegovy better for weight loss?
Clinical trials show Mounjaro achieves approximately 15–21% average weight loss versus Wegovy's approximately 15%. Both are effective, but individual results vary. The "better" option depends on your eligibility, health conditions, and personal response. A prescriber can advise which suits you after clinical assessment.
How much does Wegovy cost privately in the UK?
Private Wegovy costs approximately £129–£300 per month depending on dose and pharmacy. At the maximum dose of 2.4 mg, annual private costs range from approximately £1,500–£3,600. Prices vary between providers—always check current pricing before committing.
Can I get Mounjaro through the NHS in the UK?
Yes, Mounjaro (tirzepatide) is NICE-approved for NHS use through specialist tier 3 weight management services. However, access varies by region and waiting lists are often lengthy. Ask your GP about referral to your local NHS weight management service.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is GLP-1-only. Mounjaro may achieve slightly higher average weight loss. Both require prescription and clinical assessment. Mounjaro doses escalate to 15 mg; Wegovy to 2.4 mg. The choice depends on prescriber assessment and individual suitability.
How quickly can I access private Mounjaro or Wegovy?
Private access is typically much faster than NHS. After online consultation and prescription approval, medication is usually dispatched within 3–7 days. NHS access through specialist services can involve waiting lists of several months to over a year, depending on your region.
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.