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 Doses: How Do They Compare?
Both Wegovy and Mounjaro are prescription-only weight management injections licensed in the UK, but they have different dosing schedules. Wegovy (semaglutide) starts at 0.25 mg and escalates to a maximum of 2.4 mg weekly, while Mounjaro (tirzepatide) begins at 2.5 mg and goes up to 15 mg weekly. Understanding these dose differences can help you discuss options with your prescriber. Use our free GLP-1 weight loss calculator to explore potential 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 Dosing Schedules Compared
Wegovy (semaglutide) is a GLP-1 receptor agonist with five escalating doses over approximately 16–20 weeks:
- Week 1–4: 0.25 mg (starting dose)
- Week 5–8: 0.5 mg
- Week 9–12: 1 mg
- Week 13–16: 1.7 mg
- Week 17+: 2.4 mg (maximum maintenance dose)
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with six dose levels over approximately 20 weeks:
- Week 1–4: 2.5 mg (starting dose)
- Week 5–8: 5 mg
- Week 9–12: 7.5 mg
- Week 13–16: 10 mg
- Week 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
Both medications require a minimum of 4 weeks at each dose before escalating. Doses are administered once weekly via pre-filled injection pens — Mounjaro as a KwikPen device.
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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.
Key Dosing Differences and Clinical Implications
The main difference is that Mounjaro reaches a higher maximum dose (15 mg vs 2.4 mg), reflecting its dual mechanism of action. Clinical trials show Mounjaro may produce weight loss of approximately 15–21% of body weight, while Wegovy shows approximately 15% average weight loss — though individual results vary significantly. Your prescriber will assess your personal health and eligibility before recommending either medication. Both are prescription-only and require a clinical assessment. Track your progress with our free progress tracker once treatment begins.
- 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.
Can you switch from Wegovy to Mounjaro or vice versa?
Switching between medications must be managed by your prescriber. While approximate dose equivalencies exist (0.5 mg Wegovy ≈ 5 mg Mounjaro), there is no official conversion chart. Your prescriber may recommend a dose restart or gradual escalation if switching, depending on your individual response.
Which medication starts at a lower dose?
Wegovy starts lower (0.25 mg) than Mounjaro (2.5 mg). This reflects Wegovy's single GLP-1 mechanism versus Mounjaro's dual GIP/GLP-1 action. Lower starting doses help minimise nausea and side effects as your body adjusts.
How long does the dose escalation take for each medication?
Wegovy typically takes 16–20 weeks to reach maximum dose (2.4 mg), while Mounjaro takes approximately 20 weeks to reach 15 mg. Both require minimum 4-week intervals between dose increases, allowing your body to adjust before escalation.
Is one medication more effective than the other?
Clinical trials show both are effective for weight management. Mounjaro shows slightly higher average weight loss (15–21% vs 15%), but individual results vary. Effectiveness depends on your personal response, adherence, diet, and activity level. Your GP can advise which suits your situation.
Do both medications require the same injection frequency?
Yes — both Wegovy and Mounjaro are once-weekly injections. You inject either medication on the same day each week. Neither is a daily injection like older GLP-1 medications such as Saxenda.
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.