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 — How Do They Compare?
Mounjaro (tirzepatide) and Zepbound (tirzepatide) are the same active ingredient, but there's an important distinction: Mounjaro is the brand name used in the UK, Europe, and most of the world, while Zepbound is the US brand name. Both are dual GLP-1 and GIP receptor agonist injections for weight management. If you've seen "Zepbound" mentioned online, it's the same medication as Mounjaro — just marketed under a different name in the United States. This guide covers what Mounjaro is, how it works, and UK eligibility criteria.
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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.
Understanding Tirzepatide — One Medication, Two Brand Names
Mounjaro and Zepbound are identical medications. Both contain tirzepatide at the same doses (2.5 mg to 15 mg once weekly). The only difference is the brand name and market: Mounjaro is used in the UK, Europe, Canada, and Australia; Zepbound is the US brand name launched by Eli Lilly for the American market.
Both work as dual GIP and GLP-1 receptor agonists — a mechanism that differs from other weight loss injections like Wegovy (semaglutide), which only targets the GLP-1 pathway. This dual action may help regulate appetite, reduce cravings, and support feeling fuller after eating.
In the UK, you will always be prescribed and dispensed Mounjaro, not Zepbound. Zepbound is not available in British pharmacies — it's a US-only brand. If you see "Zepbound" mentioned in online discussions or articles, it's referring to the same tirzepatide medication you would receive as Mounjaro in the UK.
Use our GLP-1 weight loss calculator to explore potential outcomes at different doses if you're considering tirzepatide treatment.
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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.
UK Mounjaro Eligibility and How to Access It
In the UK, Mounjaro is a prescription-only medication available through NHS specialist weight management services or private prescribing. You'll be assessed based on your BMI, weight-related health conditions, and overall suitability before a prescription is issued.
NHS access: Referral to a tier 3 specialist weight management service (variable by region and waiting lists can be long). Private access: Online consultation with a licensed prescriber, typically faster, costs approximately £129–£320 per month depending on dose.
You cannot buy Mounjaro — or Zepbound — over the counter. A clinical assessment is mandatory. Your GP can discuss eligibility or refer you to specialist services. Check your BMI using our free BMI calculator to understand where you fall within NHS guidance thresholds (BMI 30+, or 27+ with weight-related conditions like type 2 diabetes or high blood pressure).
- 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 only available in the United States. In the UK, the same medication is branded as Mounjaro. You will be prescribed Mounjaro by UK pharmacies and prescribers. Zepbound cannot be imported or purchased from UK sources.
Is Mounjaro the same as Zepbound?
Yes. Mounjaro and Zepbound contain identical active ingredient (tirzepatide) at the same doses. The only difference is the brand name — Mounjaro is used in the UK and most countries; Zepbound is the US brand. Pharmacologically and clinically, they are the same medication.
How does tirzepatide (Mounjaro) work differently from Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways. Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials suggest the dual action of Mounjaro may support slightly greater average weight loss (~20.9% at maximum dose) compared to Wegovy (~14.9%), though individual results vary significantly.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is now approved by NICE for use in NHS specialist weight management services (tier 3). However, availability and waiting times vary significantly by region and ICB. Private prescribing is often faster. Both routes require a clinical assessment and prescription from a licensed prescriber.
What's the starting dose of Mounjaro in the UK?
Mounjaro starts at 2.5 mg once weekly, increasing every 4 weeks through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to a maximum of 15 mg weekly. Your prescriber will decide the escalation schedule based on your response and tolerance. This is known as dose titration.
Ready to take control of your weight loss journey?
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