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 Privately vs Wegovy — Key Differences
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available privately in the UK without NHS referral. This guide compares the two medications side by side — their mechanisms, doses, clinical trial results, and how to access them privately. Understanding the differences helps you have an informed conversation with a prescriber about which might be more suitable for your individual circumstances.
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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 Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways in the body. This dual mechanism may help regulate appetite, reduce cravings, and support feeling fuller after meals more effectively than single-pathway medications.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating the GLP-1 hormone pathway. Both medications slow gastric emptying and signal fullness to the brain, but the additional GIP activation in Mounjaro is the key mechanistic difference.
Clinical trials showed different average weight loss results: in the SURMOUNT-1 trial, Mounjaro achieved approximately clinically studied weight loss at the maximum 15mg dose. In the STEP-1 trial, Wegovy achieved approximately clinically studied weight loss at 2.4mg. However, individual results vary significantly, and trial comparisons must account for differences in study populations and duration.
- Mounjaro: starts at 2.5mg, escalates to maximum 15mg weekly
- Wegovy: starts at 0.25mg, escalates to maximum 2.4mg weekly
- Both require minimum 4 weeks at each dose before increasing
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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.
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Private Access and Prescriber Assessment
Both medications are available privately through UK-licensed prescribers via online consultation, without needing an NHS referral. A clinical assessment is required for both — a prescriber will review your BMI, weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease), current medications, and medical history to determine suitability.
Eligibility typically includes adults with BMI 30 or above, or BMI 27–29.9 with weight-related health conditions. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds (27.5+) may apply due to higher health risk profiles at those levels.
The choice between Mounjaro and Wegovy is individual and depends on your personal health profile, previous medication responses, and prescriber assessment. Both are prescription-only medicines requiring clinical review before dispensing.
- 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 showed Mounjaro achieved higher average weight loss (~21% at maximum dose vs ~15% for Wegovy). However, these are population averages — individual results vary significantly. Some people respond better to one medication than another. A prescriber will help assess which suits your circumstances based on your health profile and previous responses to similar medications.
Can I switch from Wegovy to Mounjaro privately?
Yes, some people do switch between medications. There is no official conversion chart, but approximate equivalences exist (e.g., Wegovy 1.7mg is roughly equivalent to Mounjaro 10mg). Any switch must be managed by your prescriber, who will assess your previous response and adjust accordingly. Never switch medications without professional guidance.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is GLP-1 only. The additional GIP pathway in Mounjaro may provide additional appetite regulation benefits for some people. Both work by signalling fullness to the brain and slowing digestion. The dual mechanism of Mounjaro is the primary mechanistic difference.
How much does private Mounjaro cost compared to Wegovy?
Costs vary by dose and private provider, typically ranging from £129–£320 monthly depending on the medication and dose. Mounjaro and Wegovy costs are often similar at comparable dose levels, though some providers may price them differently. Check directly with registered UK pharmacies for current pricing on your specific dose.
Do I need a GP referral to access Mounjaro or Wegovy privately?
No. Both medications are available privately through online prescribers without NHS referral. You access them directly through a private online consultation with a UK-licensed prescriber. However, informing your GP that you're using these medications is recommended so they can monitor your health and adjust any other medications if needed.
Ready to take control of your weight loss journey?
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