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 in the UK — NHS Eligibility and Prescription Guide
Mounjaro (tirzepatide) is a prescription-only weight management injection now available in the UK through both NHS specialist services and private prescribers. NICE has approved tirzepatide for use within specialist weight management services, making it one of the most widely discussed weight loss options for UK adults. Understanding your eligibility, how NHS tier 3 services work, and the differences between NHS and private access can help you make informed decisions about whether this treatment is right for you.
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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 and Tier 3 Access for Mounjaro
NHS eligibility for Mounjaro (tirzepatide) follows strict criteria set by NICE. You may qualify if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² alongside weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (from BMI 27.5). Access is through tier 3 specialist weight management services, not standard GP prescription. Your GP can refer you, but tier 3 services vary significantly by region. Some areas have well-resourced multidisciplinary teams; others have limited capacity and extended waiting lists. Once assessed by specialists, the dose titration protocol begins at 2.5 mg weekly, escalating every 4 weeks up to a maximum of 15 mg. Clinical trial data from SURMOUNT-1 showed average weight loss of 15–21% body weight across doses, though individual results vary considerably alongside dietary and activity changes.
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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.
NHS vs Private Routes — Cost, Access, and Timescales
The NHS route offers free treatment once approved, but waiting times can span months to years in many regions due to high demand and limited specialist capacity. Private prescribers and online clinics offer faster access—typically within days—but require full payment (approximately £129–£320 monthly depending on dose). Private prescribers still assess your health thoroughly before issuing a prescription; this is not a shortcut but an alternative pathway. Both routes require the Mounjaro KwikPen, stored at 2–8°C, with weekly injections. The NHS vs Wegovy comparison often arises: Mounjaro uses dual GIP and GLP-1 action, whilst Wegovy (semaglutide) acts via GLP-1 alone. Both are prescription-only. Your eligibility, prescriber recommendation, and access route (NHS or private) will determine which is suitable. Use our GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to assess your starting position.
- 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's the difference between NHS and private Mounjaro prescriptions in the UK?
NHS access is free but requires referral to tier 3 specialist services with potential waiting lists of months or longer. Private online prescribers offer faster access (days) for a fee (£129–£320 monthly). Both require clinical assessment. NHS suits those without urgency; private suits those wanting immediate access and able to pay.
Am I eligible for Mounjaro on the NHS?
You may qualify if your BMI is 30+ or 27–29.9 with weight-related health conditions (diabetes, hypertension, sleep apnoea). Lower thresholds apply if you're of South Asian, Black African, Caribbean, or Chinese heritage. Your GP can refer you to tier 3 services for formal assessment.
How long does Mounjaro take to work?
Weight loss typically begins within 2–4 weeks of starting, with noticeable effects by 8–12 weeks. Most significant loss occurs between weeks 12–20 as you reach therapeutic doses. Results vary widely and depend on diet, activity, and individual metabolism.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching is possible but requires prescriber assessment. There's no official conversion chart—approximate equivalences exist (Mounjaro 10 mg ≈ Wegovy 1.7 mg), but any change must be managed by your healthcare team. Availability depends on your tier 3 service's formulary.
What happens if I'm on a waiting list for NHS Mounjaro?
Waiting times vary by region (ICB). Whilst waiting, your GP can recommend lifestyle changes, structured diet programmes, or referral to tier 2 community services. Some people explore private options to begin treatment sooner, then transition to NHS if approved later.
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.