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 Slimming Injections — NHS Access in the UK
Mounjaro (tirzepatide) is a prescription-only slimming injection now available through NHS specialist weight management services in the UK, following NICE approval. It works as a dual GIP and GLP-1 receptor agonist, helping to regulate appetite and support weight loss alongside dietary changes and physical activity. This guide explains NHS eligibility criteria, how to access Mounjaro through the NHS, and what to expect from treatment. Use our free BMI calculator above to check your current BMI and understand where you stand on NHS eligibility 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.
NHS Access and NICE Approval for Mounjaro in the UK
NICE (National Institute for Health and Care Excellence) approved tirzepatide (Mounjaro) for use within NHS specialist weight management services in 2024. This means eligible adults can access the injection through tier 3 and tier 4 NHS weight management services, though availability varies significantly by region and integrated care board (ICB).
NHS eligibility criteria for Mounjaro:
- BMI of 30 kg/m² or above (obese category), OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, hypertension, dyslipidaemia, obstructive sleep apnoea, or established cardiovascular disease)
- For South Asian, Chinese, Black African, and Black Caribbean adults: lower thresholds apply — from BMI 27.5 kg/m²
- Must be aged 18 or over
- Commitment to lifestyle changes (diet and physical activity) alongside medication
Access is through referral to your regional NHS tier 3 specialist weight management service, usually via your GP. Waiting lists vary considerably — some areas have delays of several months to over a year.
Clinically BackedWeight Loss
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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 Access: Mounjaro Routes in the UK
NHS route: Free at point of use once prescribed by a specialist service, but involves GP referral, specialist assessment, and often significant waiting times. Availability depends on your local NHS ICB funding decisions.
Private route: Available through UK-licensed online prescribers and GPhC-registered pharmacies without NHS referral. Faster access but involves personal cost (typically £150–£300 monthly depending on dose). Both routes require clinical assessment — your prescriber will evaluate whether the Mounjaro KwikPen (the pre-filled injection device) is appropriate for your individual circumstances.
Try our free GLP-1 weight loss calculator to explore potential outcomes with Mounjaro at different doses, and use our weight converter to track progress across kg, stone, and pounds.
- 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.
How does Mounjaro work differently from other slimming injections?
Mounjaro (tirzepatide) activates two hormone pathways — GIP and GLP-1 — whereas Wegovy (semaglutide) activates only GLP-1. This dual mechanism may help with appetite regulation and food cravings. Clinical trials showed Mounjaro helped participants lose 15–21% of body weight on average, though individual results vary significantly.
What is the Mounjaro dose titration schedule on the NHS?
The standard NHS Mounjaro titration starts at 2.5 mg once weekly for 4 weeks, then increases to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg (maximum dose) — with a minimum of 4 weeks at each dose before escalation. Your NHS prescriber will adjust based on your response and tolerability.
How long do I wait for Mounjaro through the NHS?
Waiting times for NHS tier 3 specialist weight management services vary by region from a few weeks to over a year. Contact your local ICB or ask your GP about current wait times in your area. Private prescribing is typically faster — within days or weeks of assessment.
Can I switch from Wegovy to Mounjaro or vice versa on the NHS?
Medication changes are managed by your NHS specialist prescriber. Whilst approximate dose equivalences exist between tirzepatide and semaglutide, any switch requires clinical reassessment and must be done under medical supervision. Abrupt switching is not recommended.
What are the most common side effects of Mounjaro for UK patients?
Very common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain — typically mild to moderate and often improve over time. Less common but serious effects include severe stomach pain (possible pancreatitis) and gallbladder problems. Always report persistent or severe symptoms to your GP or prescriber immediately.
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.