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 vs Zepbound — What UK Patients Need to Know
If you're considering weight management injections in the UK, you may have heard of both Mounjaro and Zepbound. While Mounjaro (tirzepatide) is licensed and available in the UK through NHS specialist services and private prescribers, Zepbound is not currently approved or available in the United Kingdom. This guide explains the difference, UK eligibility criteria, and how to access weight management support through the NHS. Use our free BMI calculator to understand your starting point, and explore prescription 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.
Why Zepbound Isn't Available in the UK
Zepbound is the brand name for tirzepatide sold in the United States only. It is not licensed, approved, or available in the UK through any route — NHS or private. In the UK, the brand name for tirzepatide is Mounjaro, which is licensed by the MHRA (Medicines and Healthcare products Regulatory Authority) for weight management in adults. Zepbound was approved by the MHRA (US Food and Drug Administration) in 2023, but the UK uses its own regulatory pathway through MHRA. Different countries often use different brand names for the same active ingredient — for example, Ozempic (diabetes) and Wegovy (weight loss) are both semaglutide but sold under different brands depending on the country and indication. If you see Zepbound mentioned in UK weight loss discussions, it's typically referring to information from US sources, but UK prescribing is always through the Mounjaro brand or equivalent GLP-1 medications like Wegovy.
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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.
How to Access Weight Loss Treatment in the UK
In the UK, weight management injections are accessed through two main routes: NHS specialist services (tier 3) and private online prescribing. NHS access requires a GP referral to a specialist weight management service, where NICE-approved medications including Mounjaro may be prescribed following clinical assessment. Waiting times for NHS specialist services vary by region and can be lengthy. Private access is faster — you can have an online consultation with a UK-licensed prescriber without NHS referral. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Both routes require a full clinical assessment of your eligibility, health history, and suitability before any prescription is issued.
- 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.
Is Zepbound available in the UK?
No. Zepbound is the US brand name for tirzepatide and is not licensed or available in the UK. In the UK, tirzepatide is branded as Mounjaro and is licensed by the MHRA for weight management in adults.
What is the difference between Mounjaro and Zepbound?
There is no medical difference — both contain the same active ingredient, tirzepatide. The difference is purely the brand name and country of availability. Zepbound is sold in the United States, while Mounjaro is available in the UK and other countries.
Can I order Zepbound from a US pharmacy for use in the UK?
No. Importing prescription medications from outside the UK is illegal, and US prescriptions are not valid in the UK. You must obtain weight management medication through a UK-licensed prescriber following a UK clinical assessment.
What are my options for weight loss injections in the UK?
UK-licensed weight management injections include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Access is through NHS tier 3 specialist services or private online prescribing. Your GP can discuss eligibility and referral options with you.
How do I know if I'm eligible for Mounjaro on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Your GP can assess your individual eligibility and arrange specialist referral if appropriate.
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.