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 7.5 Mg vs Wegovy — What's the Difference?
If you're considering ordering Mounjaro 7.5 mg or comparing it with Wegovy, it helps to understand how these two prescription weight loss injections differ. Both are licensed for weight management in the UK, but they work through different mechanisms and have distinct dosing schedules. This guide breaks down the key differences between tirzepatide (Mounjaro) and semaglutide (Wegovy) to help you understand what your prescriber might recommend. Both require a clinical assessment before prescription — individual suitability varies significantly.
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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 — SURMOUNT vs STEP
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two separate hormone pathways in the body. This dual mechanism may contribute to appetite suppression and improved food satisfaction. In the SURMOUNT-1 clinical trial, participants on 7.5 mg 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 (semaglutide) is a single GLP-1 receptor agonist — it activates only the GLP-1 pathway. The STEP-1 trial showed average weight loss of approximately 14.9% body weight at the maximum dose (2.4 mg) over 68 weeks, again with lifestyle modifications.
These are clinical trial averages — individual results vary considerably. The higher average weight loss shown for Mounjaro at 7.5 mg may partly reflect the dual mechanism, though results depend on multiple factors including starting weight, adherence, and lifestyle changes.
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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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Eligibility and How to Order in the UK
Both Mounjaro and Wegovy require a UK prescription and clinical assessment. Eligibility is similar: adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes or high blood pressure. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply due to higher cardiovascular risk at lower weights.
To order Mounjaro 7.5 mg, you'll need a prescription from a UK-licensed prescriber — either through NHS specialist weight management services or a private online consultation. Your prescriber will assess whether this dose is suitable after you've completed initial lower doses (2.5 mg, then 5 mg). The KwikPen contains four weekly doses; at 7.5 mg you'd typically progress here during weeks 9–12 of treatment, depending on tolerance.
Your prescriber will consider your individual health profile, any other medications, and tolerance to lower doses before recommending a specific dose. Some people respond well at lower doses; others may benefit from titrating to higher doses. Use our free GLP-1 weight loss calculator to understand potential weight loss projections at different doses, and our BMI calculator to see where you currently stand against NHS healthy weight ranges.
- 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 7.5 mg stronger than Wegovy?
Mounjaro at 7.5 mg and Wegovy work through different mechanisms — Mounjaro has dual GIP+GLP-1 action, Wegovy has GLP-1 only. Clinical trials showed higher average weight loss with Mounjaro, but "stronger" depends on individual response. Your prescriber will recommend the medication most suitable for you based on your health profile.
Can I switch from Wegovy to Mounjaro 7.5 mg?
Yes, switching is possible, but only under prescriber guidance. There's no official conversion chart, though approximate equivalences exist (Wegovy 1.7 mg ≈ Mounjaro 10 mg). Any switch requires a new assessment and must be managed by a licensed prescriber — do not switch without clinical supervision.
How long does it take to reach Mounjaro 7.5 mg?
Mounjaro follows a dose titration schedule. You start at 2.5 mg (weeks 1–4), increase to 5 mg (weeks 5–8), then to 7.5 mg (weeks 9–12). The minimum is 4 weeks at each dose before escalation. Prescribers may adjust timings based on side effects or tolerance — this is a typical schedule, not a fixed requirement.
Can I order Mounjaro 7.5 mg without NHS?
Yes, Mounjaro is available privately through GPhC-registered online pharmacies following a clinical consultation with a UK-licensed prescriber. NHS access is through tier 3 specialist weight management services, which may have longer waiting lists. Private prescriptions typically cost £129–£320 per month depending on dose and provider.
What are the side effects at 7.5 mg Mounjaro?
Common side effects at higher doses include nausea, diarrhoea, constipation, and stomach pain — these are more frequent at higher doses. Serious but rare side effects include pancreatitis (severe stomach pain) and gallbladder problems. Side effects often reduce over time. Report persistent or severe effects to your prescriber immediately.
Ready to take control of your weight loss journey?
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