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 7.5mg vs Wegovy — Which Is Right for You?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections licensed in the UK, but they work differently and have different dose ranges. Mounjaro's 7.5mg dose represents an escalation from the starting 2.5mg, typically reached around week 9 of treatment. Understanding how Mounjaro compares to Wegovy can help you and your prescriber make an informed decision about which medication might be suitable for you. Both require a clinical assessment before prescription and work best alongside diet and lifestyle changes.
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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 Differ — Mechanism and Dosing
Mechanism of action: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways in your body. Wegovy is a GLP-1 receptor agonist only, activating a single pathway. This dual action in Mounjaro may provide additional appetite suppression and weight management support compared to single-action GLP-1 medications.
Dose escalation: Mounjaro starts at 2.5mg and can be titrated up to 15mg per week, with 7.5mg typically reached by week 9. Wegovy starts at 0.25mg and escalates to a maximum of 2.4mg per week. Higher absolute doses of Mounjaro reflect its different mechanism — it is not directly comparable to Wegovy milligram-for-milligram.
Clinical trial results: The SURMOUNT-1 trial showed Mounjaro at 15mg delivered approximately clinically studied weight loss. The STEP-1 trial showed Wegovy at 2.4mg delivered approximately clinically studied weight loss. Individual results vary significantly — these are clinical trial averages alongside reduced-calorie diet and increased physical activity.
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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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Prescriber Assessment and Individual Suitability
Both Mounjaro and Wegovy require prescription from a UK-licensed healthcare professional following a clinical assessment. Your prescriber will consider your medical history, current medications, BMI, any weight-related health conditions, and personal health goals when deciding which medication is more suitable for you. Neither medication is universally "better" — suitability depends on individual factors including contraindications, tolerability, and response to treatment.
In the UK, both medications are available through NHS specialist tier 3 weight management services (with significant regional variation and waiting lists) or through private online prescribing services following an online clinical assessment. You can use our free GLP-1 weight loss calculator to explore estimated outcomes at different doses, and our BMI calculator to understand your current health context before your consultation.
- 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 7.5mg stronger than Wegovy?
Mounjaro 7.5mg uses a dual mechanism (GIP+GLP-1) while Wegovy uses GLP-1 only, so they cannot be directly compared on dose alone. Clinical trials suggest both deliver significant weight loss, with results varying by individual. A prescriber can advise which suits your circumstances.
What is the equivalent Wegovy dose to Mounjaro 7.5mg?
There is no official established conversion between Mounjaro and Wegovy doses — they are different medications with different mechanisms. Approximate clinical equivalence suggests Mounjaro 7.5mg may be comparable to Wegovy 1.7mg, but this is not a direct swap. Any dose changes must be managed by your prescriber.
Can I switch from Mounjaro 7.5mg to Wegovy?
Switching between medications is possible but must be managed by your prescriber. You cannot simply switch at equivalent doses — your prescriber will assess whether Wegovy is appropriate and may start you on a lower dose, typically 0.25mg or 0.5mg, before titrating up.
How long does it take to reach Mounjaro 7.5mg?
Mounjaro uses a stepwise dose escalation: 2.5mg for weeks 1–4, 5mg for weeks 5–8, then 7.5mg at week 9. You must stay on each dose for at least 4 weeks before escalating. The full titration schedule takes approximately 12–16 weeks depending on tolerance and your prescriber's guidance.
Which medication causes fewer side effects — Mounjaro or Wegovy?
Both medications can cause nausea, diarrhoea, vomiting, and constipation — these are common side effects of GLP-1 and GIP/GLP-1 agonists. Individual experiences vary widely. Some people tolerate one better than the other, which is why a prescriber will assess your suitability and may adjust your dose if side effects are significant.
Ready to take control of your weight loss journey?
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