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
Do I Need A Prescription For Mounjaro In The UK?
Yes, Mounjaro (tirzepatide) is a prescription-only medicine in the UK and cannot be purchased without a valid prescription from a licensed prescriber. Whether you access it through the NHS or privately, you'll need a clinical assessment to determine if the medication is suitable for your individual health. This guide explains how UK prescribing works, who's eligible, and your options for obtaining Mounjaro through different routes.
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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.
How To Get A Mounjaro Prescription In The UK
Mounjaro prescriptions in the UK are available through two main routes: NHS specialist weight management services or private prescribing through registered online providers. The NHS route involves referral from your GP to a tier 3 or tier 4 specialist weight management service. NICE (National Institute for Health and Care Excellence) has approved tirzepatide for use within NHS weight management services, though availability varies significantly by region and ICB (Integrated Care Board). Once assessed by the specialist service, if Mounjaro is deemed appropriate, a prescription will be issued. You can check your local NHS weight management services eligibility through your GP, though waiting lists can be several months long in many areas. Privately, you can obtain a Mounjaro prescription following an online clinical consultation with a UK-licensed prescriber — a GPhC-registered pharmacy then dispenses the medication. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses before pursuing a prescription.
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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 Eligibility And NICE Guidance For Mounjaro
The NHS prescribes Mounjaro to adults meeting specific eligibility criteria: a BMI of 30 or above, or BMI 27–29.9 with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (from 27.5 or above) due to higher health risks at lower weights. NICE guidance emphasises that weight loss medications like Mounjaro should be part of a comprehensive approach including dietary changes and increased physical activity. The SURMOUNT clinical trials showed that participants using Mounjaro lost an average of 15–21% of their body weight — though individual results vary significantly. Your GP is the starting point for NHS access; they'll assess your suitability and refer you to your local specialist tier 3 service if appropriate. Use our BMI calculator to check where you fall against NHS thresholds.
- 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.
Can I buy Mounjaro without a prescription in the UK?
No. Mounjaro is a prescription-only medicine classified under UK medicines law. It cannot be legally purchased or used without a valid prescription from a licensed prescriber. Obtaining it through unlicensed channels is illegal and dangerous.
What's the difference between NHS and private Mounjaro prescriptions?
NHS prescriptions come through specialist tier 3/4 weight management services after GP referral — access is free but involves waiting lists and regional variation. Private prescriptions follow online clinical assessments with registered UK prescribers, are available faster, but require payment (typically £129–£320+ monthly depending on dose).
How long does it take to get a Mounjaro prescription on the NHS?
Timescales vary significantly by region. Some areas have waiting lists of several months to over a year for specialist weight management services. Your GP can tell you the current waiting time in your local area. Private routes typically offer prescriptions within days to a week.
Do I need to visit a hospital to get a Mounjaro prescription?
On the NHS, you'll attend a specialist weight management clinic (often in a hospital or community setting) for assessment and ongoing monitoring. Privately, initial assessment is online via video consultation, making it more convenient for many people.
What happens after I get a Mounjaro prescription — how do I use the KwikPen?
Once prescribed, you'll receive a Mounjaro KwikPen (a pre-filled injection device). You inject once weekly, rotating injection sites. Your prescriber will provide instructions; our progress tracker helps you log doses and monitor results alongside diet and activity changes.
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.