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 for Weight Loss on the NHS
Mounjaro (tirzepatide) is a prescription-only weekly injection that has been approved by NICE for weight management within NHS specialist services in the UK. It's a dual GIP and GLP-1 receptor agonist — meaning it works through two different hormone pathways to help reduce appetite and support weight loss. Access via the NHS is through tier 3 specialist weight management services, though regional availability and waiting times vary considerably across the UK.
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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.
How Mounjaro Works for Weight Loss
Mounjaro's dual mechanism sets it apart from other weight loss injections. It activates both the GIP receptor (glucose-dependent insulinotropic polypeptide) and the GLP-1 receptor, which work together to regulate appetite, reduce food cravings, and help you feel fuller after smaller meals. The medication also slows how quickly food moves through your stomach, though this effect typically reduces over time. In the SURMOUNT clinical trials, participants using Mounjaro alongside a reduced-calorie diet and increased physical activity lost an average of 15–21% of their body weight — though individual results vary significantly. It is delivered as a once-weekly injection (the Mounjaro KwikPen) and requires dose titration, starting at 2.5 mg and escalating up to a maximum of 15 mg weekly.
Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses, and our BMI calculator to establish your starting point for NHS assessment.
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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 Access: Eligibility and the Tier 3 Pathway
On the NHS, Mounjaro is accessed through specialist tier 3 (or tier 4) weight management services, not standard GP prescriptions. NICE has approved tirzepatide for use within these services for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds due to higher health risks at these weights. Access requires a GP referral to your local integrated care board's (ICB) specialist weight management service. Waiting times vary widely by region — some areas have waiting lists of several months. Check with your GP about current availability and waiting times in your area.
- 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.
Can I get Mounjaro on the NHS for weight loss?
Yes, Mounjaro is NICE-approved for weight management within NHS tier 3 specialist services. Access is through a GP referral to your local specialist weight management service, not direct from your GP. Availability and waiting times vary significantly by region. Your GP can advise on the current pathway in your area.
What's the difference between Mounjaro and Wegovy on the NHS?
Both are licensed for weight management, but Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, while Wegovy (semaglutide) is a single GLP-1 agonist. Mounjaro showed slightly higher average weight loss in trials (15–21% vs 15%). Access routes are similar, though availability varies. A prescriber will assess which is more suitable for you.
How long does it take to see weight loss results with Mounjaro on the NHS?
Weight loss typically begins within the first 4 weeks, with more noticeable changes by 8–12 weeks. The medication works gradually alongside lifestyle changes. Maximum effects are usually seen after 4–6 months at your target dose. Individual timelines vary, and your specialist service will monitor progress regularly.
What weight-related health conditions qualify me for Mounjaro on the NHS?
Type 2 diabetes or prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, and history of heart attack or stroke can all qualify you if your BMI is 27–29.9. If your BMI is 30 or above, you may be eligible regardless of other conditions. A specialist will assess your individual case.
Is there a private alternative if NHS waiting lists are too long?
Yes, Mounjaro is available through private prescription-only routes following an online clinical assessment with a UK-licensed prescriber. Private access usually has shorter waiting times but involves a cost, typically £129–£250+ per month depending on dose and provider. Your GP can advise on NHS alternatives if waiting times are extended.
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.