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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Tirzepatide Injection on the NHS in the UK
Tirzepatide is a weekly weight loss injection now approved for use within the NHS in the UK. Also known by its brand name Mounjaro, this dual GIP and GLP-1 receptor agonist has been cleared by NICE (National Institute for Health and Care Excellence) for use in specialist weight management services. NHS access differs significantly from private prescribing, with eligibility criteria and a structured pathway through tier 3 services. Understanding how NHS tirzepatide works and whether you might qualify can help you explore your options with your GP.
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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 and Tier 3 Weight Management Services
NICE approved tirzepatide (Mounjaro) for use within specialist tier 3 weight management services across England, Scotland, Wales, and Northern Ireland. To access tirzepatide on the NHS, you must be referred by your GP to your local integrated care board (ICB) weight management service, not prescribed directly in primary care.
You may be eligible if you have:
- BMI of 30 kg/m² or above (obesity), or
- BMI of 27–29.9 kg/m² (overweight) with at least one weight-related condition such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease
- For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply (from BMI 27.5)
Clinical trial data from SURMOUNT-1 showed participants lost an average of 15–21% body weight over 72 weeks on tirzepatide doses ranging from 5 mg to 15 mg weekly, alongside reduced-calorie diet and increased physical activity. NHS referrals typically involve assessment of your health history, previous weight loss attempts, and readiness for medication alongside lifestyle change.
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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 Access vs. Private Tirzepatide Prescribing in the UK
NHS route: Referral through your GP to a tier 3 specialist weight management service. Assessment by a multidisciplinary team, prescription and monitoring provided by the NHS, no cost to you. However, waiting times for tier 3 services vary significantly by region—some areas have waiting lists of several months to over a year due to demand.
Private route: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a GPhC-registered pharmacy. Available without NHS referral, faster access, but costs range from approximately £129–£320 per month depending on dose and provider.
Both routes require a clinical assessment to confirm you meet eligibility criteria and that tirzepatide is safe for you. Your GP can discuss which route may be suitable for your circumstances. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
- 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 do I access tirzepatide (Mounjaro) on the NHS in the UK?
Ask your GP for a referral to your local integrated care board (ICB) tier 3 specialist weight management service. You cannot be prescribed tirzepatide directly in primary care. The specialist service will assess your eligibility based on BMI, health conditions, and previous weight loss attempts. Once approved, the NHS provides the injection and ongoing monitoring at no cost. Waiting times vary by region.
What are the NHS eligibility criteria for tirzepatide?
You typically need a BMI of 30 or above, or 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify from a lower BMI (27.5) due to higher metabolic health risks. Your GP or specialist service will assess your individual circumstances.
Is tirzepatide available on the NHS for everyone?
No. Tirzepatide is available through specialist tier 3 NHS weight management services, not through standard primary care. Availability and waiting times vary by region and ICB. Some areas have very long waiting lists. Your GP can explain what's available in your area and discuss both NHS and private options.
How much weight can I expect to lose on tirzepatide on the NHS?
Clinical trials showed an average loss of 15–21% body weight over 72 weeks, but individual results vary significantly. Weight loss depends on the dose you're prescribed, adherence to the injection, dietary changes, physical activity, and personal factors like age, metabolism, and existing health conditions. Your specialist team will monitor your progress.
What's the difference between getting tirzepatide on the NHS versus privately in the UK?
NHS access is through tier 3 specialist services after GP referral; it's free but may involve waiting lists. Private prescribing is faster and doesn't require NHS referral, but costs £129–£320 per month depending on dose. Both require clinical assessment. Your GP can help you decide which route suits your circumstances.
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.