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 vs Mounjaro Dose — What's the Difference?
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight loss injections available in the UK, but they work on different mechanisms and use different dosing schedules. Wegovy starts at a lower dose and escalates more gradually, while Mounjaro begins at 2.5 mg and reaches a higher maximum. Understanding how each dose progression works can help you discuss options with your GP or prescriber. Both require clinical assessment before prescription, and individual results vary significantly. Use our GLP-1 weight loss calculator to explore projected outcomes at different doses.
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Calculate Your BMI Instantly
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.
Wegovy and Mounjaro Dose Schedules Compared
Wegovy (semaglutide) is a GLP-1 receptor agonist starting at 0.25 mg once weekly and escalating to a maximum of 2.4 mg once weekly over approximately 16 weeks. Each dose is held for 4 weeks before increasing. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist beginning at 2.5 mg once weekly and reaching a maximum of 15 mg once weekly, also requiring minimum 4-week intervals between dose increases.
- Wegovy: 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg (5-step escalation)
- Mounjaro: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg (6-step escalation)
The key difference is Mounjaro's higher maximum dose and dual mechanism targeting two hormone pathways, whereas Wegovy targets only GLP-1. Clinical trials showed Mounjaro produced slightly higher average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight), though individual responses vary considerably.
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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.
Choosing Between the Two — Key Considerations
Both medications are prescription-only and require a clinical assessment from a UK-licensed prescriber before dispensing. Eligibility includes adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions. Access is available through NHS specialist weight management services or private online prescribing. Your prescriber will assess which medication suits your individual health profile, medical history, and any other medications you take. Try our BMI calculator to check your current category, and use the GLP-1 weight loss calculator to estimate potential outcomes at different doses with either medication.
- 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 starting dose for Wegovy compared to Mounjaro?
Wegovy starts at 0.25 mg once weekly, while Mounjaro starts at 2.5 mg once weekly. Both escalate gradually over several weeks. The higher starting dose for Mounjaro reflects its dual mechanism (GIP+GLP-1), whereas Wegovy's lower starting dose (GLP-1 only) allows gentler titration.
Which injection reaches a higher maximum dose?
Mounjaro reaches a maximum of 15 mg once weekly, significantly higher than Wegovy's 2.4 mg maximum. The higher maximum reflects Mounjaro's dual receptor agonist action and may contribute to slightly greater average weight loss in clinical trials.
Do both medications require the same time between dose increases?
Yes, both require a minimum of 4 weeks at each dose level before escalating. This allows your body to adjust and helps identify the optimal dose with the least side effects for you personally.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between these medications is possible but must be managed by your prescriber. There is no official established conversion chart — approximate equivalences exist (e.g., Wegovy 2.4 mg roughly corresponds to Mounjaro 15 mg), but any switch requires medical oversight and reassessment.
Which medication is more readily available on the NHS in the UK?
Both are NICE-approved for UK NHS use, but availability varies significantly by region and waiting lists can be lengthy. Private access is often faster and does not require NHS referral. Your GP can advise on local NHS options and specialist service waiting times.
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.