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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Mounjaro Trials & How to Access in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection backed by clinical trials showing significant results. If you're considering this medication in the UK, understanding the trial evidence, eligibility criteria, and how to access it—whether through NHS specialist services or private prescription—is essential. This guide covers the SURMOUNT trials, UK costs, and what to expect from the application process.
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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.
Mounjaro Clinical Trials & Access Routes in the UK
The SURMOUNT-1 clinical trial demonstrated that tirzepatide helped participants lose an average of 15% to 21% of their body weight over 72 weeks, depending on the dose, alongside a reduced-calorie diet and increased physical activity. The trial included over 2,500 adults with obesity or overweight with weight-related health conditions, establishing the evidence base for UK licensing.
In the UK, you can access Mounjaro through two main routes: NHS specialist services (typically tier 3 weight management clinics) or private prescription through GPhC-registered online pharmacies. NHS access requires GP referral and assessment by a specialist weight management team, though availability and waiting times vary significantly by region. Private access is faster—available without NHS referral—and involves a UK-licensed prescriber conducting an online clinical assessment.
- NHS route: free on prescription but longer waiting times in many areas
- Private route: available within days, costs vary by dose (typically £129–£250+ monthly)
- Both routes require a clinical assessment to confirm eligibility
- Maximum dose: 15 mg once weekly; dose titration takes 4+ weeks
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: Costs, Eligibility & What to Expect
NHS access: Mounjaro is available through NICE-approved NHS weight management services for adults with BMI ≥30, or BMI 27–29.9 with weight-related health conditions. However, NHS availability is patchy—some regions have long waiting lists, others offer limited access. You'll need GP referral to a tier 3 service, assessment, and ongoing monitoring.
Private access: Online consultations typically cost £20–£40, with medication costs ranging from £129 (5 mg dose) to £250+ (15 mg dose) per month, depending on the provider and dose strength. The Mounjaro KwikPen contains four weeks of injections. Private providers assess your health history, confirm eligibility, and issue a prescription within 24–48 hours if approved. Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different tirzepatide doses.
- 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 much weight did people lose in the SURMOUNT trials?
In SURMOUNT-1, participants on tirzepatide lost an average of 15% of body weight on 5 mg, 19.5% on 10 mg, and 20.9% on 15 mg over 72 weeks. Results were achieved with lifestyle changes. Individual results vary—some lost more, some less.
What's the difference between NHS and private Mounjaro access?
NHS is free but requires GP referral and specialist assessment, with regional waiting lists. Private is faster (48 hours to prescription) but costs £129–£250+ per month. Both require clinical eligibility assessment.
How long does dose titration take with Mounjaro?
Dose titration takes a minimum of 16 weeks to reach the maximum 15 mg dose. You start at 2.5 mg for 4 weeks, then increase by 2.5 mg every 4 weeks. Your prescriber may adjust timing based on side effects or response.
Is Mounjaro available on the NHS in all UK regions?
No. NHS availability varies by integrated care board (ICB). Some regions have established Mounjaro services; others have waiting lists of many months. Check with your GP about local availability and expected waiting times.
What happens if I want to switch from Mounjaro to Wegovy?
Switching between tirzepatide and semaglutide requires prescriber guidance. Approximate equivalence exists (15 mg Mounjaro ≈ 2.4 mg Wegovy), but individual needs vary. Your prescriber will assess suitability and manage the transition safely.
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.