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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Where to Buy Mounjaro in the UK — Mounjaro vs Wegovy
If you're searching for where to buy Mounjaro in the UK, you'll need a prescription from a licensed prescriber — it's available through NHS specialist weight management services or private online consultations. Wegovy is another UK-licensed weight loss injection you may have heard of, and while both are effective prescription medicines, they work differently and suit different people. This guide compares where to access each, how they differ, and helps you understand which might be 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.
How Mounjaro and Wegovy Work — Key Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two different hormone pathways in your body. This dual mechanism may help regulate appetite more effectively and support faster initial weight loss in some people. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single pathway. Both are once-weekly injections, but Mounjaro starts at 2.5 mg and goes up to 15 mg, whilst Wegovy starts at 0.25 mg and reaches a maximum of 2.4 mg.
- SURMOUNT trial data (Mounjaro): average weight loss of approximately 15–21% body weight at the highest doses
- STEP trial data (Wegovy): average weight loss of approximately 15% body weight
- Both are most effective alongside a reduced-calorie diet and increased physical activity
- Individual results vary significantly between people
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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
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Where to Get Mounjaro and Wegovy — Access in the UK
Both Mounjaro and Wegovy require a prescription from a UK-licensed prescriber — you cannot buy either without a clinical assessment. On the NHS, access is through specialist tier 3 weight management services, usually via GP referral. Waiting times vary significantly by region and can be lengthy. Privately, both are available through GPhC-registered online pharmacies following an online consultation with a prescriber. The prescriber will assess your BMI, health history, and any weight-related conditions to decide which medication — if either — suits you best. Individual suitability depends on your health profile, not just availability.
- 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.
Can I buy Mounjaro or Wegovy without a prescription in the UK?
No. Both are prescription-only medicines that require a clinical assessment from a UK-licensed prescriber before they can be dispensed. You must have a valid prescription from a doctor or registered prescriber to obtain either medication.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist (two hormone pathways), whilst Wegovy is a GLP-1 receptor agonist only (one pathway). Clinical trials suggest Mounjaro may help some people lose slightly more weight on average, but individual results vary significantly.
Which is cheaper — Mounjaro or Wegovy?
Costs vary by dose and private provider. On average, Mounjaro and Wegovy have similar monthly costs (roughly £129–£320 privately, depending on dose). NHS access is free but involves waiting lists and regional variation. Your prescriber can discuss costs with you.
How long does it take to see weight loss results with these injections?
Most people notice reduced appetite within the first 1–2 weeks. Measurable weight loss typically begins within 4–8 weeks, but the full effect builds over several months. It takes 16–20 weeks to reach your target dose with either medication.
Can my GP prescribe Mounjaro or Wegovy, or do I need a specialist?
NHS prescribing is through specialist tier 3 weight management services, not usually your GP directly. Privately, any UK-licensed prescriber can assess and issue a prescription following an online or in-person consultation. Ask your GP about NHS referral options in your area.
Ready to take control of your weight loss journey?
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