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 Research: What UK Evidence Shows
Mounjaro (tirzepatide) is backed by substantial clinical research, and the NHS has now approved it for weight management through specialist services. This guide explains what the research shows, how NHS eligibility works, and how the evidence translates to UK healthcare. Whether you're considering Mounjaro through the NHS or privately, understanding the evidence and access routes helps you make an informed decision with your GP or prescriber.
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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.
NHS Eligibility and Clinical Evidence for Mounjaro
The SURMOUNT trials are the foundation of Mounjaro's approval. SURMOUNT-1, the key trial, showed that adults taking tirzepatide 15 mg alongside a reduced-calorie diet and increased physical activity lost an average of 20.9% of their body weight over 72 weeks — significantly more than placebo or semaglutide (Wegovy). Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
NHS eligibility criteria: You may access Mounjaro through NHS tier 3 specialist weight management services if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds (27.5+) apply due to higher metabolic risk.
NICE approval: The National Institute for Health and Care Excellence (NICE) has recommended tirzepatide as cost-effective for NHS use, but access varies significantly by region and specialist service availability. Waiting lists for tier 3 services can be lengthy in many areas.
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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 to Mounjaro in the UK
NHS route: Referral to a tier 3 weight management service through your GP, clinical assessment by a multidisciplinary team, prescription issued if eligible, and medication dispensed by the NHS. This is free at point of use but involves waiting lists and regional availability differences.
Private route: Online consultation with a UK-licensed prescriber, clinical assessment via video or questionnaire, prescription issued if appropriate, and dispensed by a GPhC-registered pharmacy. Private access is faster (often days rather than months) but costs approximately £150–£320 monthly depending on dose. Both routes require a prescription and individual health assessment—tirzepatide is not available without one. Check your BMI and personal eligibility using our free BMI calculator above.
- 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 does the SURMOUNT-1 trial show about Mounjaro weight loss?
SURMOUNT-1 found that adults on Mounjaro 15 mg lost an average of 20.9% of body weight over 72 weeks, compared to 3% on placebo. Results were better than semaglutide. However, individual results vary significantly. Weight loss was achieved alongside a reduced-calorie diet and increased physical activity.
Am I eligible for Mounjaro on the NHS in the UK?
You may be eligible if you have a BMI of 30+ or 27–29.9 with weight-related health conditions (diabetes, hypertension, cardiovascular disease). South Asian, Chinese, Black African, and Caribbean adults may qualify at BMI 27.5+. Access is through NHS tier 3 specialist weight management services, not standard GP prescription.
How long is the NHS waiting list for Mounjaro?
Waiting times vary significantly by region and local ICB (Integrated Care Board). Some areas have waiting lists of several months to over a year. Private access is typically faster—often available within days to weeks through online prescribers and GPhC-registered pharmacies.
Is tirzepatide the same as Mounjaro?
Yes. Tirzepatide is the active ingredient; Mounjaro is the brand name. Tirzepatide is a dual GIP and GLP-1 receptor agonist, which differs from semaglutide (Wegovy), which activates GLP-1 only. The SURMOUNT trials demonstrated tirzepatide's effectiveness in producing greater weight loss than semaglutide.
What does the NHS research show about Mounjaro side effects?
Research shows common side effects include nausea, diarrhoea, constipation, and vomiting—most often during the initial weeks. Serious side effects are rare but may include pancreatitis. NHS prescribers monitor patients throughout treatment. Individual tolerance varies; starting at lower doses (2.5 mg) helps minimise early side effects.
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.