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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7.5 Mg Mounjaro vs Wegovy — How Do They Compare?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections licensed in the UK, but they work differently. At 7.5 mg, Mounjaro is an escalation dose in the titration schedule, whereas Wegovy at equivalent effectiveness typically uses its 1.7 mg or 2.4 mg maintenance doses. Understanding the differences between these two medications — their mechanisms, clinical trial results, and eligibility — can help you and your prescriber decide which might be suitable for you. Both require a clinical assessment before being prescribed.
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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.
Mechanism and Trial Data — Key Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. This dual mechanism may contribute to its average weight loss of approximately 19.5% body weight at the 10 mg dose in the SURMOUNT-1 trial, and around 20.9% at the maximum 15 mg dose. At 7.5 mg, the escalation dose, average weight loss was approximately 15.7% in clinical trials.
Wegovy (semaglutide) is a single GLP-1 receptor agonist. In the STEP-1 trial, it achieved approximately 14.9% average body weight loss at the maximum 2.4 mg dose. Both medications were studied alongside a reduced-calorie diet and increased physical activity — results vary significantly between individuals.
- Mounjaro: dual mechanism (GIP + GLP-1)
- Wegovy: single mechanism (GLP-1 only)
- Both: prescription-only, once-weekly injections
- Neither: clinically studied weight loss outcomes
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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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Dose Equivalence and Individual Suitability
At 7.5 mg, Mounjaro is roughly equivalent to Wegovy 1.7 mg in terms of clinical effect, though these are approximate comparisons and not an official conversion chart. Your prescriber will assess your individual health, eligibility, BMI, any weight-related conditions, and response to treatment to determine which medication and dose is suitable. Use our free BMI calculator to check your starting point, and discuss both options with your GP or a licensed prescriber. Side effects, personal medical history, and previous medication responses all influence the choice. Neither medication is "better" — suitability is individual.
- 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 7.5 mg Mounjaro the same strength as Wegovy?
No. 7.5 mg Mounjaro is approximately equivalent to Wegovy 1.7 mg in clinical effect, though this is not an official conversion. Both are prescription-only and work through different mechanisms — Mounjaro uses dual GIP+GLP-1 activation, while Wegovy uses GLP-1 only. Any switch between medications must be managed by a prescriber.
Which caused more weight loss in clinical trials?
Mounjaro at its maximum 15 mg dose showed slightly higher average weight loss (~20.9%) compared to Wegovy 2.4 mg (~14.9%) in their respective trials. However, individual results vary considerably, and the trial conditions (diet and exercise support) were different. Clinical trial averages do not predict individual outcomes.
Are side effects different between Mounjaro and Wegovy?
Both share common side effects including nausea, diarrhoea, vomiting, and constipation — particularly during dose escalation. Mounjaro may have slightly different tolerability due to its dual mechanism. Your GP can discuss which side effect profile might suit you better based on your medical history.
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications requires prescriber guidance. There is no standard conversion protocol — your prescriber will assess your response to the first medication and determine if a switch is appropriate, and if so, at what dose. This is a clinical decision, not a self-managed change.
How do I know which injection is right for me?
Your prescriber will assess your BMI, weight-related health conditions, previous medication responses, and individual circumstances. Both require a clinical assessment before prescription. Our GLP-1 weight loss calculator can show you potential outcomes, but your prescriber's personalised assessment is essential for the right choice.
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.