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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Does Wegovy Work The Same As Mounjaro? UK Access & Cost Guide
Wegovy and Mounjaro are both licensed weight loss injections available in the UK, but they work through different mechanisms. While both are GLP-1 based medications, Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whereas Wegovy (semaglutide) activates only the GLP-1 pathway. This means they affect your appetite and metabolism slightly differently, though clinical trial results are comparable. Understanding how each works, their costs, and how to access them in the UK will help you make an informed decision with your prescriber.
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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 Wegovy And Mounjaro Differ In Mechanism And Cost
Wegovy (semaglutide) activates a single hormone pathway—GLP-1 receptor agonism—which signals fullness to the brain and slows gastric emptying. Mounjaro (tirzepatide) works on two pathways simultaneously: GIP (glucose-dependent insulinotropic polypeptide) plus GLP-1 activation. This dual mechanism may explain why some clinical trial participants on Mounjaro experienced slightly greater average weight loss (approximately 15–21% body weight) compared to Wegovy users (approximately 14.9% at the maximum dose). However, individual results vary significantly. In the UK, Wegovy costs approximately £129–£180 per month for maintenance doses through private prescribing, depending on dose strength and provider. Mounjaro typically costs £150–£240 per month privately, also dose-dependent. Both require a prescription following a clinical assessment from a UK-licensed prescriber, and neither is available without a prescription.
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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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NHS Vs Private Access: How To Get Wegovy Or Mounjaro In The UK
NHS route: Both medications are available through specialist tier 3/4 weight management services, but access varies significantly by region and NHS waiting lists can be lengthy (sometimes months to over a year). Your GP can refer you to your local specialist weight management service, but availability depends on your integrated care board (ICB).
Private route: Both Wegovy and Mounjaro are available through UK-registered online prescribing services. You complete an online health questionnaire, have a consultation with a UK-licensed prescriber (GP or nurse prescriber), and if approved, receive a prescription dispensed by a GPhC-registered pharmacy. This typically takes 1–3 days. Private access does not require NHS referral, making it faster for many people. Use our free GLP-1 weight loss calculator to estimate potential results with either medication.
- 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 Mounjaro more effective than Wegovy for weight loss?
Clinical trials show Mounjaro produced slightly higher average weight loss (15–21% vs 14.9% for Wegovy), but results vary individually. The dual GIP/GLP-1 mechanism may work better for some people, while others respond equally well to Wegovy's single GLP-1 pathway. Your prescriber can help determine which is more suitable for you.
What's the cost difference between Wegovy and Mounjaro in the UK?
Privately, Wegovy typically costs £129–£180 per month, while Mounjaro ranges from £150–£240 per month, depending on your dose and provider. Both are available through NHS specialist services at no cost to eligible patients, though waiting times and regional availability vary considerably.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official conversion chart—switching requires a new clinical assessment and gradual dose adjustment with the new medication. Never switch without consulting your doctor or prescriber.
How long does it take to get Wegovy or Mounjaro on the NHS?
NHS waiting times vary dramatically by region, ranging from several months to over a year in some areas. Check with your local integrated care board (ICB) for current waiting lists. Private prescribing typically takes 1–3 days from consultation to delivery.
Do I need a prescription for either Wegovy or Mounjaro in the UK?
Yes, both are prescription-only medicines. You cannot purchase either without a valid UK prescription from a licensed prescriber. Private online prescribers can issue prescriptions following a health assessment, but a prescription is always required by law.
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.