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 Medicine in the UK — How It Works and NHS Access
Mounjaro is a prescription-only injectable medicine containing tirzepatide, licensed in the UK for weight management in adults. It's a dual GIP and GLP-1 receptor agonist — meaning it works on two natural hormone pathways to help regulate appetite and support weight loss alongside diet and exercise. Access to Mounjaro in the UK varies: it's available through NHS specialist weight management services in some areas, and through private online prescribing following clinical assessment. Understanding how Mounjaro works, who's eligible, and your access options will help you make an informed decision about whether it's right for you.
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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 NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services in England and Wales. You may be eligible for NHS prescription if you have 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, high blood pressure, high cholesterol, sleep apnoea, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (from BMI 27.5 or above) due to higher health risks at lower weights. Access is through tier 3 specialist weight management services — not standard GP prescription. You'll need a referral from your GP and a clinical assessment by the specialist team. Availability varies significantly by region and NHS Integrated Care Board (ICB), and waiting lists can be lengthy in many areas. Use our free BMI calculator above to check whether you fall within the eligibility range for your height.
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 Access to Mounjaro in the UK
If NHS waiting lists are long or you don't meet local eligibility criteria, Mounjaro is available privately through GPhC-registered online pharmacies. Private access requires an online clinical assessment from a UK-licensed prescriber who will review your health history, BMI, and weight-related conditions to determine suitability. Private prescriptions are typically processed faster than NHS, though costs range from approximately £150–£250 per month depending on dose. Both routes require a valid prescription from a licensed prescriber — Mounjaro is not available over-the-counter. Whichever route you choose, the medicine itself is identical, and clinical monitoring remains important to assess whether the medication is working for you and managing side effects effectively.
- 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 medicine and how does it work?
Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist that mimics natural hormones released after eating. It helps regulate appetite, reduce food cravings, and support feeling fuller after meals. It's given as a once-weekly injection using a pre-filled KwikPen device. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly.
Who is eligible for Mounjaro on the NHS in the UK?
You may be eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Access is through tier 3 specialist weight management services via GP referral — not standard GP prescription. Availability varies by region.
What's the difference between Mounjaro and Wegovy?
Both are prescription-only weight management injections licensed in the UK. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist with a maximum dose of 15 mg weekly. Wegovy (semaglutide) is a GLP-1 agonist only with a maximum dose of 2.4 mg weekly. Both showed similar average weight loss in clinical trials. The choice depends on individual suitability, determined by a prescriber following clinical assessment.
How much does Mounjaro cost on the NHS compared to private?
On the NHS, Mounjaro is available free if prescribed through tier 3 specialist services, though access is limited by waiting lists and regional availability. Privately, costs typically range from £150–£250 per month depending on dose. Private access is faster but requires payment. Your GP can discuss both options and referral to NHS specialist services if appropriate.
What are the main side effects of Mounjaro?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — usually mild and temporary. Common side effects include indigestion, fatigue, dizziness, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or allergic reactions. Your prescriber will discuss risks versus benefits before starting. See our Mounjaro side effects UK guide for full details.
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.