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
When Did Mounjaro Come Out in the UK?
Mounjaro (tirzepatide) was approved in the UK in November 2023 by the MHRA (Medicines and Healthcare products Regulatory Authority) for weight management in adults. It became available for prescription through the NHS and private online prescribing services shortly after. Mounjaro is a once-weekly injectable medication that works differently from older weight loss treatments — it's a dual GIP and GLP-1 receptor agonist. Understanding its timeline helps you see where this medication fits in the broader weight management landscape. Use our free GLP-1 weight loss calculator to explore how Mounjaro might fit your health goals.
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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 Approval Timeline — From USA to UK
Mounjaro was initially approved in the United States by the MHRA in May 2022 for weight management. The UK approval process followed, with the MHRA granting approval in November 2023. This timeline reflects the standard regulatory pathway between MHRA and MHRA approval. Following NICE (National Institute for Health and Care Excellence) guidance, the NHS began integrating tirzepatide into specialist weight management services in early 2024, though regional availability varies. Private online prescribing services began offering Mounjaro shortly after MHRA approval. The medication comes as a pre-filled KwikPen device with four weekly doses per pen. Access requires a UK prescription from a licensed prescriber following a clinical assessment — it is not available over-the-counter. Our free BMI calculator can help you determine whether you may fall within NHS eligibility criteria for this medication.
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.
How Mounjaro Compares to Wegovy (Older GLP-1 Treatment)
Wegovy (semaglutide), a GLP-1-only medication, came to the UK market before Mounjaro in 2021. Mounjaro's key difference is its dual mechanism — it activates both GIP and GLP-1 pathways, whereas Wegovy activates GLP-1 alone. Clinical trials showed Mounjaro resulted in slightly higher average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight). Both are prescription-only, once-weekly injections. Mounjaro vs Wegovy is a common question — your GP or prescriber will assess which medication, if either, is appropriate for your individual circumstances. Individual results vary significantly, and either medication is typically used alongside reduced-calorie diet and increased physical activity for best outcomes.
- 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, Mounjaro (tirzepatide) is available through NHS specialist tier 3 weight management services for eligible adults. Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. However, NHS availability and waiting times vary significantly by region. Many people access it through private online prescribing services.
What's the difference between Mounjaro and Ozempic?
Both contain similar semaglutide-type mechanisms but in different forms. Mounjaro is tirzepatide (dual GIP+GLP-1), while Ozempic is semaglutide (GLP-1 only) and approved for type 2 diabetes, not weight loss. Wegovy is the UK-licensed weight management semaglutide version. Always ensure you're prescribed the correct, licensed medication for your health goal.
How quickly does Mounjaro start working?
Most people begin noticing changes within 2–4 weeks, though Mounjaro works gradually. The medication is titrated (dose increased slowly) over 16–20 weeks to reach the maximum dose. Full effects are typically observed after reaching a stable, therapeutic dose. Individual responses vary significantly.
Can I get Mounjaro privately in the UK without NHS referral?
Yes. Private online prescribing services offer Mounjaro following a remote clinical assessment with a UK-licensed prescriber. If a prescription is issued, you can collect it through a GPhC-registered pharmacy. Costs vary by provider and dose, typically ranging from £129–£320 per month depending on your starting and current dose.
What were the main clinical trials that proved Mounjaro works?
The SURMOUNT-1 trial (published 2023) demonstrated Mounjaro's effectiveness. Participants at 15mg dose achieved approximately 20.9% average body weight loss over 72 weeks alongside diet and exercise. Results varied individually. NHS and NICE decisions were based on this evidence alongside safety data and cost-effectiveness analysis.
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.