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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How Many People Are On Mounjaro In The UK?
Mounjaro (tirzepatide) uptake in the UK has increased significantly since NICE approval, though exact prescription numbers remain limited. Unlike the US, where millions have access to GLP-1 and dual GIP/GLP-1 medications, UK prescription rates are constrained by NHS availability and private access costs. This guide compares Mounjaro adoption with Wegovy across the UK and explains eligibility criteria. Use our free BMI calculator to check whether you might qualify for either prescription weight loss medication based on NHS thresholds.
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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 vs Wegovy: UK Prescription Uptake And Clinical Trials
Exact UK prescription numbers for Mounjaro are not publicly released, but uptake has accelerated since NICE approved tirzepatide for weight management in 2023. Wegovy (semaglutide) has been available longer, suggesting higher cumulative numbers, though neither medication dominates UK weight loss treatment — most people still access weight management through NHS lifestyle services or privately-prescribed alternatives.
Clinical trial context: The SURMOUNT-1 trial (Mounjaro's key efficacy study) involved approximately 1,200 participants, with average weight loss of 20.9% at the maximum 15 mg dose over 72 weeks. The STEP-1 trial (Wegovy) studied approximately 1,900 participants, showing 14.9% average weight loss at 2.4 mg over 68 weeks. Both trials included reduced-calorie diet and increased physical activity — medication alone does not drive results.
- Mounjaro is a dual GIP + GLP-1 receptor agonist (two hormone pathways)
- Wegovy is a GLP-1-only receptor agonist (single pathway)
- Both require prescription and clinical assessment before dispensing
- Individual results vary significantly — trial averages do not predict personal outcomes
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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.
UK Access Routes: NHS Specialist Services vs Private Prescription
NHS access: Mounjaro and Wegovy are available through specialist tier 3 and tier 4 weight management services following GP referral. However, availability is highly variable by region (Integrated Care Board). Many areas have lengthy waiting lists — access can take months or longer. NHS prescribing is restricted to specific eligibility criteria and requires assessment by a multidisciplinary team.
Private access: Both medications are available through GPhC-registered online pharmacies following a clinical consultation with a UK-licensed prescriber. Private access does not require NHS referral but involves out-of-pocket costs (typically £129–£320 per month depending on dose). A prescriber will assess your individual suitability, not assures prescription. Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses alongside your prescriber discussion.
- 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 more widely used than Wegovy in the UK?
No exact figures are published, but Wegovy has been available longer (approved 2021) suggesting higher cumulative prescriptions. Mounjaro (approved 2023) uptake is growing. Both remain niche treatments compared to overall NHS weight management provision. Actual prescriber preference varies by region and individual suitability.
What's the difference between Mounjaro and Wegovy mechanisms?
Mounjaro (tirzepatide) activates two hormone pathways: GIP and GLP-1, which may explain slightly higher average weight loss in trials (20.9% vs 14.9%). Wegovy activates GLP-1 only. However, individual response varies — one medication is not objectively "better", prescriber assessment determines suitability.
How many people are eligible for Mounjaro in the UK?
Millions could theoretically qualify (BMI ≥30, or ≥27 with weight-related health conditions), but actual prescription numbers are constrained by NHS availability, waiting lists, and private costs. Most eligible people do not currently access these medications.
Can I get Mounjaro on the NHS in the UK?
Yes, through specialist weight management services after GP referral. However, availability varies dramatically by region — some areas have extensive waiting lists. Private prescription is faster but requires personal payment. Your GP can advise on local NHS access or suggest private options.
How does Mounjaro's KwikPen dose titration work compared to Wegovy?
Mounjaro starts at 2.5 mg, increasing weekly to 15 mg maximum. Wegovy starts at 0.25 mg, increasing over 16 weeks to 2.4 mg maximum. Mounjaro reaches high doses faster. Both require minimum time at each dose. Prescriber guidance determines your personal schedule based on tolerability.
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.