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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Wegovy Dose Compared to Mounjaro: Key Differences
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight loss injections licensed in the UK, but they work via different mechanisms and have different dose ranges. Understanding how the two compare can help you discuss options with your GP or prescriber. Individual suitability depends on your health profile, and either medication requires a clinical assessment before prescription. This guide breaks down the dose schedules, trial data, and how to decide which might be appropriate for you.
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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.
Dose Schedules and Trial Results Compared
Wegovy (semaglutide) is a GLP-1 receptor agonist only, with doses escalating from 0.25 mg to a maximum of 2.4 mg once weekly. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, with doses ranging from 2.5 mg to 15 mg once weekly — a significantly higher dose range reflecting its dual mechanism.
Clinical trial data shows average weight loss results: in the STEP-1 trial, Wegovy achieved approximately clinically studied weight loss at the 2.4 mg dose. In the SURMOUNT-1 trial, Mounjaro achieved approximately 15% at 5 mg, 19.5% at 10 mg, and 20.9% at the 15 mg dose. However, individual results vary considerably, and these are clinical trial averages alongside reduced-calorie diet and increased physical activity.
- Wegovy escalation: 4 weeks at each dose, starting 0.25 mg
- Mounjaro escalation: 4 weeks at each dose, starting 2.5 mg
- Both are once-weekly injections via pre-filled pens
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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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Mechanism Differences and Suitability Factors
The key difference is mechanism: Wegovy activates only the GLP-1 pathway, while Mounjaro activates both GIP and GLP-1 receptors. This dual action in Mounjaro may contribute to greater weight loss in some individuals, though both medications reduce appetite and support feeling fuller after smaller meals.
Your suitability for either medication depends on your individual health profile, existing medical conditions, and how your body responds. A UK-licensed prescriber will assess whether Mounjaro or Wegovy is more appropriate following a clinical consultation. Both require a prescription and eligibility assessment. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and discuss trial data with your prescriber to understand realistic expectations for your situation.
- 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.
What is the maximum dose of Wegovy compared to Mounjaro?
Wegovy's maximum dose is 2.4 mg once weekly, while Mounjaro's maximum is 15 mg once weekly. The higher dose range for Mounjaro reflects its dual GIP+GLP-1 mechanism versus Wegovy's single GLP-1 mechanism. Both are once-weekly injections started at lower doses and escalated gradually.
Which causes more weight loss, Wegovy or Mounjaro?
Clinical trials suggest Mounjaro may produce slightly higher average weight loss (up to 20.9%) compared to Wegovy (approximately 14.9%), but individual results vary significantly. Trial data shows both are effective, and suitability depends on your health profile. Your prescriber will help determine which is appropriate for you.
How long does each dose escalation take?
Both medications follow a 4-week escalation schedule at each dose level. With Wegovy, you start at 0.25 mg and progress through five doses to reach 2.4 mg. With Mounjaro, you start at 2.5 mg and can escalate to 15 mg. Each dose is given once weekly.
Can you switch from Wegovy to Mounjaro or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official established conversion chart — approximate equivalences exist (e.g., Mounjaro 5 mg is roughly equivalent to Wegovy 0.5 mg), but any switch requires clinical assessment and personalised guidance from your doctor or prescriber.
Are Wegovy and Mounjaro both available on the NHS in the UK?
Both medications are licensed in the UK and available through NHS specialist weight management services (tier 3), though regional availability and waiting lists vary significantly. Both are also available privately following an online clinical assessment with a UK-licensed prescriber. Your GP can advise on NHS access in your area.
Ready to take control of your weight loss journey?
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