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 Results — What the Evidence Shows
Mounjaro (tirzepatide) is a prescription-only weight loss injection available in the UK through NHS specialist services and private prescribing. Clinical trials show that people taking Mounjaro lost an average of 15–21% of their body weight over 72 weeks — though individual results vary significantly. Weight loss depends on your starting weight, dose, lifestyle changes, and how your body responds. This guide explains what UK research and NHS guidance tell us about realistic Mounjaro results and how to access it through the NHS.
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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 Access and Clinical Evidence for Mounjaro in the UK
NICE approval and NHS access: The UK's National Institute for Health and Care Excellence (NICE) has approved tirzepatide (Mounjaro) for weight management in NHS specialist tier 3 and tier 4 services. This means access is through dedicated weight management clinics, not standard GP prescription. Eligibility requires a BMI of 30 or above (or 27+ with weight-related health conditions), and prescribing must follow clinical assessment.
Clinical trial results: The SURMOUNT-1 trial, which forms the evidence base for UK approval, showed:
- 5 mg dose: Average weight loss of ~15% body weight (approximately 10–15 kg for most adults)
- 10 mg dose: Average weight loss of ~19.5% body weight (approximately 14–20 kg)
- 15 mg dose: Average weight loss of ~20.9% body weight (approximately 15–25 kg)
These results were achieved alongside a reduced-calorie diet and increased physical activity. Results typically continue improving through the full 72-week trial period. Use our GLP-1 weight loss calculator above to estimate potential results based on your starting weight and dose, though remember individual outcomes vary.
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.
Realistic Expectations and NHS vs Private Routes
Individual variation is significant: Some people lose 5–10% body weight, others achieve 25%+ loss. Factors affecting results include starting weight (larger individuals often lose more in absolute kg), genetics, adherence to diet and exercise, dose reached, and how long you stay on treatment. NHS guidance emphasises that medication works best alongside sustained lifestyle changes — diet alone or injections alone produce less impressive results than the combination.
NHS vs private access: On the NHS, you'll access Mounjaro through a specialist tier 3 weight management service following GP referral. Waiting lists vary by region, sometimes lasting months. Private online prescribers offer faster access but require upfront payment. Both routes require clinical assessment and prescription — Mounjaro cannot be bought without a valid prescription from a UK-licensed healthcare professional.
- 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's the average weight loss with Mounjaro on the NHS?
Clinical trials showed average weight loss of 15–21% body weight over 72 weeks at maintenance doses. This typically equates to 10–25 kg depending on starting weight, though individual results vary significantly. Results continue improving the longer you remain on treatment, particularly during dose escalation phases.
How long does it take to see results from Mounjaro?
Most people notice appetite changes within 1–2 weeks of starting. Measurable weight loss typically becomes apparent after 4–8 weeks. Significant weight loss (5–10% body weight) usually takes 12–16 weeks. Maximum results are typically seen by 16–24 weeks on a stable dose.
Will I lose weight on Mounjaro without changing my diet?
Clinical trial results were achieved alongside a reduced-calorie diet and increased physical activity. Mounjaro alone, without lifestyle changes, produces less weight loss. NHS guidance emphasises that medication is a tool to support dietary and exercise changes, not a replacement for them.
Can I get Mounjaro on the NHS for weight loss?
Yes, NICE has approved tirzepatide (Mounjaro) for NHS use in specialist tier 3 weight management services. Eligibility requires BMI ≥30 (or ≥27 with weight-related conditions). You'll need referral from your GP to a specialist service. Availability and waiting times vary significantly by region.
How does Mounjaro compare to other weight loss injections like Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist (tirzepatide), while Wegovy is a GLP-1 agonist only (semaglutide). SURMOUNT trials showed Mounjaro achieved 15–21% average weight loss, while STEP trials showed Wegovy achieved approximately 14.9% average weight loss. Both are prescription-only and results vary individually.
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.