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 in the UK — What You Need to Know
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK for adults with obesity or overweight with related health conditions. This NHS health guide explains how Mounjaro works, who may be eligible, typical doses, side effects, and how to access it through NHS services or private prescribing. Our free BMI calculator and weight converter help you understand your current health status in UK measurements. This information is educational only and does not replace advice from your GP.
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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 and What Makes It Different
Mounjaro is a dual GIP and GLP-1 receptor agonist — this dual mechanism sets it apart from other weight loss injections. It works by activating two natural hormone pathways that help regulate appetite and food cravings. Many users report feeling fuller after smaller meals, which supports reduced calorie intake alongside healthy weight management.
Unlike insulin, Mounjaro does not directly lower blood sugar but helps your body use glucose more effectively. It also slows how quickly food leaves your stomach, though this effect typically reduces over time. The medication is administered as a once-weekly injection using a pre-filled KwikPen device. Clinical trials showed that on average, participants lost between 15% and 21% of their body weight — though individual results vary significantly depending on lifestyle, diet, and other factors.
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.
UK Eligibility and NHS Access Pathways
In the UK, you may be eligible for Mounjaro if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or heart disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidance recommends lower BMI thresholds due to higher health risks at lower weights.
Access through the NHS requires referral to a tier 3 specialist weight management service — this is not available as a standard GP prescription. Regional ICB availability varies significantly, and waiting lists can be lengthy. Private access is available through UK-licensed prescribers following an online clinical assessment. Any prescriber will assess your individual health before issuing a prescription.
- 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.
Is Mounjaro available on the NHS in the UK?
Yes, NICE has approved tirzepatide (Mounjaro) for NHS use, but access is through specialist tier 3 weight management services, not standard GP prescription. You'll need referral from your GP, and availability varies by region. NHS waiting lists can be lengthy. Private prescribing is also available through GPhC-registered services.
What are the typical Mounjaro doses used in the UK?
Mounjaro starts at 2.5 mg weekly for four weeks, then escalates every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum. Your prescriber adjusts the dose based on tolerability and response. Most people take between 5 mg and 15 mg as maintenance dose.
What are the most common side effects of Mounjaro?
Nausea, diarrhoea, constipation, and stomach pain are very common, especially when starting or increasing dose. Most side effects improve over time. Injection site reactions, fatigue, and reduced appetite are also reported. Serious side effects are rare but include severe stomach pain (possible pancreatitis) — seek urgent medical attention if this occurs.
Can I get Mounjaro through a private prescription in the UK?
Yes, you can obtain Mounjaro through private online prescribing with a UK-licensed prescriber. After a clinical assessment, if approved, a prescription is dispensed by a GPhC-registered pharmacy. You can use MyWeightCheck's free BMI calculator and weight loss calculator to understand your current health context before consultation.
How does Mounjaro compare to other weight loss injections like Wegovy?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist; Wegovy (semaglutide) is GLP-1 only. Clinical trials show Mounjaro averaged 15–21% weight loss versus Wegovy's ~15%. Both are once-weekly injections, prescription-only, and used alongside diet and exercise. Results vary individually — your prescriber will discuss which suits you. ---
Ready to take control of your weight loss journey?
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