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 10mg vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections licensed in the UK. At the 10mg dose, Mounjaro works through a dual mechanism—activating both GIP and GLP-1 hormone pathways—whilst Wegovy uses a single GLP-1 pathway. Clinical trial data shows different efficacy profiles, but which is more suitable depends entirely on your individual health, prescriber assessment, and how your body responds. This guide compares the two medications factually, helping you understand the key differences. Use our free BMI calculator above to establish your baseline, then discuss options with your GP or licensed 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.
Trial Data and How They Work Differently
Mounjaro's dual mechanism: At 10mg, tirzepatide activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors. In the SURMOUNT-1 clinical trial, participants taking 10mg Mounjaro lost an average of approximately 19.5% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy's single mechanism: Semaglutide activates GLP-1 receptors only. The STEP-1 trial showed participants lost approximately 14.9% of body weight on the maximum 2.4mg dose at 68 weeks with the same lifestyle support.
- Mounjaro reaches 10mg; Wegovy's maximum is 2.4mg—different dose ranges reflect different mechanisms
- Individual results vary significantly; trial averages do not predict personal outcomes
- Both require a reduced-calorie diet and physical activity to work effectively
- Onset of appetite reduction typically occurs within 1–2 weeks for both
Neither medication is a substitute for lifestyle changes—both are tools used alongside dietary modifications and exercise.
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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.
Side Effects and Suitability — Which Is Right for You?
Both medications share common side effects: nausea, diarrhoea, constipation, and stomach pain are reported by many users, particularly during dose escalation. Mounjaro may cause hair loss more frequently; Wegovy users sometimes report headaches. Serious side effects like pancreatitis or gallbladder problems are rare but require immediate medical attention.
Suitability depends on:
- Your eligibility (BMI 30+ or 27+ with weight-related health conditions)
- Whether you have type 2 diabetes or prediabetes (both help, but Mounjaro's dual action may offer additional glycaemic control)
- Your prescriber's assessment and clinical judgment
- Your response to the medication—some individuals respond better to one than the other
- Cost and NHS/private access in your region
Your GP or licensed prescriber will assess your individual health profile to determine which is appropriate. There is no universal "better" option—only which is better suited to you. Use our GLP-1 weight loss calculator to explore potential weight loss projections at different doses to inform your discussion with your prescriber.
- 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 10mg stronger than Wegovy?
Mounjaro 10mg and Wegovy's maximum (2.4mg) use different mechanisms and dose ranges, so direct strength comparison is not straightforward. In clinical trials, Mounjaro 10mg showed approximately 19.5% average weight loss versus Wegovy's 14.9%, but individual results vary significantly. Your prescriber will determine which mechanism and dose is appropriate for your health profile.
Can I switch from Wegovy to Mounjaro at 10mg?
A prescriber can consider switching medications, but there is no official established conversion chart. Approximate equivalence places Mounjaro 10mg in the range of Wegovy's 1.7–2.4mg, but any switch must be managed by your prescriber. You would typically start at a lower Mounjaro dose and titrate upwards.
What's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. This dual mechanism in Mounjaro may help regulate appetite differently and may offer additional benefits for blood sugar control. Both are prescription-only and require clinical assessment.
How long does it take to see results on Mounjaro 10mg?
Most users notice appetite reduction within 1–2 weeks of starting or increasing their dose. Meaningful weight loss typically becomes apparent after 4–8 weeks on a stable dose, combined with reduced-calorie diet and physical activity. Results vary between individuals—some lose more quickly, others more gradually.
Can my GP prescribe Mounjaro 10mg on the NHS?
Mounjaro is available through NHS specialist tier 3 weight management services following referral from your GP, though regional availability and waiting times vary significantly. You can also access it privately through a licensed prescriber and GPhC-registered pharmacy following an online clinical assessment. Availability and cost differ between these routes.
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.