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 Weight Loss on the NHS in the UK
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection now approved for use within NHS specialist weight management services. If you're considering Mounjaro through the NHS or want to understand how it works, this guide explains NHS eligibility, the approval process, expected weight loss, and how it differs from other weekly weight loss injections like Wegovy. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential results at different doses.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
How Mounjaro Works for Weight Loss
Mounjaro is a dual GIP and GLP-1 receptor agonist—meaning it activates two natural hormone pathways in your body that regulate appetite and food intake. Unlike single-action medications, this dual mechanism may help reduce hunger, lower food cravings, and help you feel fuller after smaller meals. The medication also slows gastric emptying (how quickly food leaves your stomach), though this effect typically reduces over time. In the SURMOUNT-1 clinical trial, adults taking the maximum dose of Mounjaro (15 mg once weekly) lost an average of approximately 20.9% of their body weight over 72 weeks—though individual results vary significantly. Weight loss was achieved alongside a reduced-calorie diet and increased physical activity, not Mounjaro alone. Your GP or prescriber will explain realistic expectations for your individual situation.
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 Eligibility and Access for Mounjaro
NHS eligibility for Mounjaro: NICE (National Institute for Health and Care Excellence) has approved tirzepatide for use within NHS specialist tier 3 and tier 4 weight management services. You typically need a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds (27.5+) due to higher health risks at lower weights. Access is through specialist referral only—not standard GP prescription. Availability and waiting times vary significantly by region and integrated care board (ICB). Many areas have substantial waiting lists. Convert your weight using our free weight converter to check your current BMI category.
- 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 is the difference between Mounjaro and Wegovy for weight loss?
Both are prescription-only once-weekly weight loss injections. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro's dual mechanism may provide stronger appetite suppression. Clinical trials show Mounjaro achieved ~clinically studied weight loss vs Wegovy's ~15%, though individual results vary. Both work best alongside diet and exercise changes.
How long does it take to see weight loss results with Mounjaro on the NHS?
Weight loss typically begins within the first few weeks, but most significant results are seen after 12–16 weeks of treatment as your dose increases. The SURMOUNT trial measured results over 72 weeks. Consistency with diet, physical activity, and staying on your prescribed dose matters. Results vary between individuals.
What is the maximum dose of Mounjaro for weight loss?
The maximum dose is 15 mg once weekly. Dosing starts at 2.5 mg and increases by 2.5–5 mg every 4 weeks, reaching 15 mg after approximately 20 weeks. Your prescriber may adjust based on your response and tolerance. Not everyone needs or reaches the maximum dose.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications requires prescriber guidance. There is no official conversion chart—approximate equivalence exists (Wegovy 2.4 mg roughly equals Mounjaro 10 mg), but any switch must be managed individually. Discuss with your NHS specialist weight management service if you're considering a change.
How much weight can I expect to lose with Mounjaro on the NHS?
Individual results vary significantly based on starting weight, diet, activity level, genetics, and medication dose. Clinical trials showed average loss of 15–21% of body weight over 72 weeks. This might mean 10–20 kg for some people, though outcomes differ. Your GP or specialist can give personalised estimates based on your circumstances.
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.