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
Free tracker included with every download this week
Mounjaro Official Information for UK Adults
Mounjaro is the brand name for tirzepatide, a prescription-only weekly injection licensed in the UK for weight management in adults. Unlike some other weight loss medications, Mounjaro works as a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to help regulate appetite and support feeling fuller after meals. This page explains what Mounjaro officially is, how it works, eligibility criteria in the UK, available doses, and how to access it through NHS specialist services or private prescribing routes.
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 and What Makes It Different
Mounjaro (tirzepatide) is fundamentally different from older weight loss injections because it activates two hormone systems rather than one. The GIP receptor and GLP-1 receptor both play roles in appetite regulation and blood sugar control. When activated together, they may help reduce food cravings, support smaller portion sizes, and slow gastric emptying (how quickly food leaves the stomach). Clinical trials showed that participants using Mounjaro lost an average of 15–21% of their body weight over 72 weeks—though individual results vary significantly based on dose, lifestyle changes, and personal factors.
Mounjaro comes as a KwikPen pre-filled injection device that you use once weekly. Doses range from 2.5 mg (starting dose) up to 15 mg (maximum). Each pen contains four weekly doses. Use our free GLP-1 weight loss calculator above to explore how different doses may affect projected weight loss outcomes.
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 How to Access Mounjaro
In the UK, Mounjaro may be prescribed for adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, abnormal cholesterol, or cardiovascular disease). South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds due to higher health risk profiles at the same weight.
Access Mounjaro through two routes: NHS specialist weight management services (tier 3), requiring GP referral and often involving waiting lists; or private online prescribing through GPhC-registered pharmacies following a clinical assessment. Always consult your GP or a licensed prescriber to assess whether Mounjaro is appropriate for your individual circumstances.
- 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 the same as Ozempic or Wegovy?
No. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist made by Eli Lilly. Wegovy (semaglutide) is a GLP-1-only injection from Novo Nordisk. Ozempic is also semaglutide but approved for diabetes, not weight loss. All are prescription-only, but Mounjaro's dual mechanism may offer different effects than single GLP-1 injections.
What is the starting dose of Mounjaro?
The starting dose is 2.5 mg once weekly for the first four weeks. After this adjustment period, doses typically increase every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum. Your prescriber determines your dose based on your response and tolerability.
How much weight can I expect to lose on Mounjaro?
Clinical trials (SURMOUNT-1) showed average weight loss of 15–21% of body weight at 72 weeks, depending on dose—but individual results vary significantly. Weight loss occurs alongside reduced-calorie diet and increased physical activity. Use our GLP-1 weight loss calculator to see estimated projections based on your starting weight.
Can I get Mounjaro through the NHS in the UK?
Yes. Mounjaro is available through NHS specialist tier 3 weight management services. Access requires a GP referral and clinical assessment. Availability and waiting times vary significantly by region and local integrated care boards. Private access through online prescribing is also available without NHS referral.
What are the most common side effects of Mounjaro?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain—especially when starting or increasing doses. Most side effects reduce over time. Seek urgent medical attention for severe persistent abdominal pain (possible pancreatitis) or serious allergic reactions. Always discuss side effects with your prescriber.
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.