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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When Was Mounjaro Released in the UK?
Mounjaro (tirzepatide) was approved by the MHRA and released in the UK in November 2023 for weight management in adults. This dual GIP and GLP-1 receptor agonist injection became available through both NHS specialist services and private prescribing pathways. Understanding the timeline of its release helps explain why it has become an increasingly common option in UK weight management. Use our free BMI calculator to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes with Mounjaro.
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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.
Mounjaro's Release Timeline and Approval Journey
Mounjaro's approval pathway: Tirzepatide was first approved by the MHRA in the United States in November 2021 for weight management, followed by European regulatory approval. The MHRA approved Mounjaro for use in the UK in November 2023, making it available to UK adults who meet eligibility criteria. This UK approval came after positive data from the SURMOUNT clinical trials, which demonstrated that tirzepatide helped participants lose an average of 15–21% of their body weight when combined with reduced-calorie diet and increased physical activity. Individual results vary significantly depending on the dose and individual response. Unlike Mounjaro, the related injection Wegovy (semaglutide) was approved for UK weight management earlier. The tirzepatide KwikPen device became the standard delivery method, offering a convenient once-weekly injection format that UK patients find straightforward to use at home.
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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.
What Mounjaro's Release Means for UK Patients
Since November 2023, Mounjaro has been available through two main UK routes: NHS specialist tier 3 weight management services (following a GP referral) and private online prescribing through GPhC-registered pharmacies. Access varies significantly by region due to NHS capacity and ICB funding decisions. NICE initially recommended Mounjaro within NHS specialist services, though availability remains limited in many areas. The release of this dual-action GLP-1/GIP medication gave UK patients an additional licensed option alongside Wegovy and Saxenda. To understand if Mounjaro might be suitable, try our free BMI calculator to check your BMI category and eligibility threshold, then speak with your GP or a licensed prescriber about your options.
- 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 and when did it become available in the UK?
Mounjaro (tirzepatide) is a prescription-only weight management injection that was approved by the MHRA in November 2023. It's a dual GIP and GLP-1 receptor agonist administered once weekly via the KwikPen device. It became available through NHS specialist services and private prescribing.
How does Mounjaro differ from Wegovy?
Mounjaro uses a dual GIP/GLP-1 mechanism, while Wegovy (semaglutide) uses GLP-1 only. Clinical trials showed Mounjaro produced slightly higher average weight loss (15–21% vs ~15% for Wegovy). Both are prescription-only and require clinical assessment. Individual results vary.
Was Mounjaro approved by the NHS immediately after its November 2023 release?
NICE reviewed and recommended Mounjaro for use within NHS specialist weight management services, but NHS availability varies by region. Many areas have significant waiting lists. Private prescribing became available more immediately through online pathways following clinical assessment.
How long does Mounjaro take to work after starting?
Most people notice appetite changes within the first few weeks. Significant weight loss typically becomes apparent after 8–12 weeks of consistent use at an effective dose. Weight loss continues over months as doses are increased. Results vary between individuals.
Can I get Mounjaro on the NHS now?
Mounjaro is available through NHS tier 3 specialist weight management services if you meet eligibility criteria and are referred by your GP. Access depends on your region and local commissioning. Private prescribing is also available. Speak with your GP about your options.
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.