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 Injection: NHS Access & UK Prescribing
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection licensed in the UK for adults with obesity or overweight with weight-related health conditions. In the NHS, access is through specialist tier 3 weight management services following NICE guidance. This guide explains UK eligibility criteria, how NHS prescribing works, the difference between NHS and private routes, and what to expect. Mounjaro is administered as a weekly KwikPen injection and is increasingly available through both NHS specialist services and private prescribing in 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.
NHS Eligibility & NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for use within NHS weight management services. Eligibility in the NHS typically requires a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, prediabetes, hypertension, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower eligibility thresholds starting at BMI 27.5 due to higher metabolic risk at lower weights. Access is through specialist NHS tier 3 or tier 4 weight management services, not standard GP prescription. Waiting lists for these services vary significantly by region and ICB (Integrated Care Board). Our free BMI calculator above can help you determine whether you may meet initial eligibility criteria, though a full assessment by a healthcare professional is required.
- Requires referral from your GP to specialist weight management services
- Clinical assessment by a specialist team before prescription
- Treatment alongside reduced-calorie diet and increased physical activity
- Regular monitoring and dose titration over 16–20 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 Routes to Mounjaro in the UK
NHS route: Through tier 3 specialist weight management services following GP referral. Free on prescription but subject to regional availability and waiting lists, which can exceed 6–12 months in many areas.
Private route: Through GPhC-registered online prescribers following an online clinical assessment. Available without NHS referral, faster access (typically within 1–2 weeks), but costs approximately £130–£280 per month depending on dose. Both routes require a prescription from a UK-licensed prescriber. Our GLP-1 weight loss calculator above can help you estimate potential outcomes at different Mounjaro doses, and our progress tracker helps log results once treatment begins.
- 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 Mounjaro (tirzepatide) and how does it work for weight loss?
Mounjaro is a prescription-only, once-weekly injection that acts as a dual GIP and GLP-1 receptor agonist. It activates two natural hormone pathways to help regulate appetite, reduce food cravings, and support feeling fuller after meals. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly.
What are the NHS eligibility criteria for Mounjaro in the UK?
The NHS typically prescribes Mounjaro to adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions like type 2 diabetes or hypertension. Lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults (BMI 27.5+). Assessment must be done by a specialist NHS weight management service, not your GP.
How long are NHS waiting lists for Mounjaro, and what's the cost?
NHS waiting times vary significantly by region and ICB, ranging from 3–12+ months. Mounjaro is free on NHS prescription once approved. Private access costs £130–£280 monthly depending on dose and provider, with faster turnaround (1–2 weeks) but requires payment.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription-only UK-licensed weight loss injections, but Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1-only agonist. Mounjaro has a slightly higher maximum dose (15 mg vs 2.4 mg) and showed marginally higher average weight loss in trials (~21% vs ~15%), though results vary individually.
Can I get Mounjaro on the NHS if I don't meet the standard BMI criteria?
Possibly, if you have significant weight-related health conditions. A GP referral to your local NHS tier 3 weight management service is the first step—they'll assess your individual circumstances. However, NHS access is more limited than private access, which may offer Mounjaro with a lower BMI threshold following a private clinical assessment.
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.