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 vs Mounjaro: Dosage Comparison
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections available in the UK, but they have different dosing schedules and maximum doses. Wegovy starts at 0.25 mg and escalates to a maximum of 2.4 mg weekly, while Mounjaro begins at 2.5 mg and reaches a maximum of 15 mg weekly. Understanding the dosing differences can help you have an informed conversation with your GP or prescriber about which option might be appropriate for you. Both are once-weekly injections requiring clinical assessment before prescription.
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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.
Dosing Schedules: Week-by-Week Breakdown
Wegovy (semaglutide) dosing schedule: Treatment begins at 0.25 mg weekly for the first four weeks, then increases by 0.25 mg every four weeks. Week 5–8: 0.5 mg, weeks 9–12: 1 mg, weeks 13–16: 1.7 mg, and from week 17 onwards: 2.4 mg (maximum maintenance dose). Each dose is administered as a once-weekly injection using a pre-filled pen.
Mounjaro (tirzepatide) dosing schedule: Treatment starts at 2.5 mg weekly and escalates at four-week intervals. Weeks 5–8: 5 mg, weeks 9–12: 7.5 mg, weeks 13–16: 10 mg, weeks 17–20: 12.5 mg, and from week 21 onwards: 15 mg (maximum dose). Like Wegovy, Mounjaro is administered once weekly using the KwikPen device. Not everyone requires escalation to the maximum dose — your prescriber will assess the right dose for your individual needs.
Our GLP-1 weight loss calculator can help you explore projected weight loss outcomes at different doses based on clinical trial data, though individual results vary.
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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
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Key Differences and Choosing Between Them
The main difference is mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy activates GLP-1 only. This means they work through slightly different hormonal pathways. In clinical trials, Mounjaro showed slightly higher average weight loss (approximately 15–21% of body weight) compared to Wegovy (approximately 15%), though individual results vary significantly. Dosing also differs — Mounjaro's doses are higher in mg terms but that reflects its dual mechanism. Neither is "better" — suitability depends on your health history, any other medications you take, and how your body responds. Your GP or prescriber will assess your eligibility based on UK criteria (BMI ≥30, or ≥27 with weight-related health conditions) and recommend the most appropriate option. Access is available through NHS specialist weight management services or private prescribing.
- 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's the difference between Wegovy and Mounjaro dosing?
Wegovy (semaglutide) starts at 0.25 mg and titrates to a maximum of 2.4 mg weekly over 16 weeks. Mounjaro (tirzepatide) starts at 2.5 mg and reaches 15 mg weekly over 20 weeks. Both are once-weekly injections, but Mounjaro's doses are higher because it activates two hormone pathways rather than one.
Which medication has higher maximum doses?
Mounjaro has a maximum dose of 15 mg weekly, whilst Wegovy's maximum is 2.4 mg weekly. The difference reflects their different mechanisms — Mounjaro is a dual GIP/GLP-1 agonist, whilst Wegovy is GLP-1 only. Higher dose numbers don't necessarily mean stronger effect.
How long does it take to reach the maximum dose?
Wegovy reaches maximum (2.4 mg) in approximately 16 weeks (4 months). Mounjaro reaches maximum (15 mg) in approximately 20 weeks (5 months). Both increase every four weeks if tolerated. Your prescriber may keep you at a lower maintenance dose if it's working well for you.
Is Ozempic the same as Wegovy?
No. Both contain semaglutide but Ozempic is licensed for type 2 diabetes (doses up to 2 mg) and is not licensed for weight loss in the UK. Wegovy is the specific licensed weight management formulation (up to 2.4 mg). Using Ozempic for weight loss would be off-label prescribing.
Can I switch between Wegovy and Mounjaro?
Switching between them must be managed by your prescriber — there's no official conversion chart. Approximate equivalences exist based on clinical practice (e.g. Mounjaro 5 mg ≈ Wegovy 0.5 mg), but any switch requires medical supervision to ensure safety and effectiveness.
Ready to take control of your weight loss journey?
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