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 by Eli Lilly: NHS Access and UK Prescribing
Mounjaro is a prescription-only weight management injection manufactured by Eli Lilly and approved by the MHRA for use in the UK. It's a dual GIP and GLP-1 receptor agonist that may help reduce appetite and support weight loss when combined with dietary changes and increased physical activity. Unlike generic versions or unregulated products, Mounjaro is available through NHS specialist services and private online prescribing in the UK, following proper clinical assessment. Understanding how it works and how to access it can help you decide if it's right for you.
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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.
NHS Eligibility, NICE Approval and the Prescribing Pathway
NICE approved Mounjaro (tirzepatide) for use within NHS specialist weight management services, though availability varies significantly by region. Eligibility typically requires a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, hypertension, or obstructive sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds due to increased health risks at lower body weights. Access is through tier 3 NHS specialist weight management services, not standard GP prescribing—you'll need a referral from your GP and assessment by the specialist team. The KwikPen delivery device allows easy once-weekly injections at home, with doses starting at 2.5 mg and titrating up to a maximum of 15 mg. NHS waiting lists can be lengthy in many areas, sometimes taking months to years from referral to first prescription.
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.
NHS vs Private Access: Routes and Realistic Expectations
NHS route: Free on prescription but requires GP referral to specialist services, clinical assessment, and significant waiting times. Private route: Available through UK-registered online prescribers and GPhC pharmacies without NHS referral—typically faster access but involves costs from £129–£320+ per month depending on dose. Both routes require a proper clinical assessment to confirm you meet eligibility criteria and that Mounjaro is safe for you. Once prescribed, you'll track your progress using our free progress tracker, monitor your BMI with our free BMI calculator, and work with your prescriber on dose adjustments. Individual results vary—clinical trials showed average weight loss of 15–21% of body weight at different doses, but outcomes depend on your starting weight, lifestyle changes, and individual response. Your GP remains your first point of contact for advice about which route is right for your 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.
What exactly is Mounjaro, and who manufactures it?
Mounjaro (tirzepatide) is a prescription-only weight management injection made by Eli Lilly, a major global pharmaceutical company. It's a dual GIP and GLP-1 receptor agonist—meaning it works via two hormone pathways to help regulate appetite and blood sugar. It's administered once weekly via a pre-filled KwikPen injector and is MHRA-approved for adults in the UK.
Can I get Mounjaro on the NHS, and how long does it take?
Yes, NICE has approved Mounjaro for NHS specialist weight management services, but access varies by region and waiting lists are often long (months to years in some areas). You need a GP referral to a tier 3 specialist weight management service, which will assess your eligibility and manage your treatment. Private access is faster but involves costs.
Who is eligible for Mounjaro on the NHS in the UK?
Generally, adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions like type 2 diabetes or hypertension. South Asian and other ethnic groups have lower BMI thresholds (27.5+). Your GP can discuss whether you meet local eligibility criteria.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1-only agonist. Both are once-weekly injections, but Mounjaro may offer greater appetite suppression due to its dual mechanism. Clinical trials showed slightly higher average weight loss with Mounjaro, though results vary between individuals.
How can I estimate my potential weight loss with Mounjaro?
Our GLP-1 weight loss calculator above can help you project potential outcomes at different doses based on clinical trial data. Remember that individual results vary significantly and depend on your lifestyle changes, starting weight, and personal response. Always discuss realistic expectations 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.