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: Dose Comparison Guide
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK, but they work differently and use different dose ranges. Wegovy is a GLP-1 receptor agonist, while Mounjaro is a dual GIP and GLP-1 agonist — this difference affects how much medication you need. Understanding the dose ranges, starting points, and titration schedules can help you have an informed conversation with your prescriber about which medication might be suitable for you. 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.
Dose Ranges and Titration Schedules
Wegovy (semaglutide) starts at 0.25 mg once weekly and escalates gradually to a maximum of 2.4 mg. The full titration takes approximately 16 weeks:
- Weeks 1–4: 0.25 mg
- Weeks 5–8: 0.5 mg
- Weeks 9–12: 1 mg
- Weeks 13–16: 1.7 mg
- Week 17 onwards: 2.4 mg (maintenance)
Mounjaro (tirzepatide) starts at a higher initial dose (2.5 mg) and escalates to a maximum of 15 mg. The Mounjaro kwikpen titration takes approximately 20 weeks:
- Weeks 1–4: 2.5 mg
- Weeks 5–8: 5 mg
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21 onwards: 15 mg (maximum)
Both use once-weekly injections. The key difference is that Mounjaro reaches higher total doses because of its dual mechanism — tirzepatide activates two hormone pathways rather than one.
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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.
Weight Loss Outcomes and Approximate Equivalence
In clinical trials, Wegovy achieved average weight loss of approximately 14.9% of body weight at the 2.4 mg dose (68 weeks, STEP-1 trial), while Mounjaro achieved approximately 15–21% depending on final dose (SURMOUNT-1 trial). These are averages — individual results vary significantly. Approximate dose equivalence: Wegovy 0.5 mg ≈ Mounjaro 5 mg; Wegovy 1.7 mg ≈ Mounjaro 10 mg; Wegovy 2.4 mg ≈ Mounjaro 15 mg. However, there is no official conversion chart, and any switch between medications must be managed by your prescriber. Both are most effective when combined with dietary changes and increased physical activity. Check your BMI and explore projected outcomes using our free weight loss calculator above.
- 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 at an equivalent dose?
Not directly without prescriber guidance. Although approximate dose equivalences exist (Wegovy 1.7 mg ≈ Mounjaro 10 mg), there is no official NHS or manufacturer conversion chart. Any switch must be managed by your prescriber, who may adjust doses based on your individual response and tolerance. Never self-switch between medications.
Which medication requires a lower starting dose?
Wegovy starts lower at 0.25 mg, while Mounjaro starts at 2.5 mg. This doesn't mean Mounjaro is "stronger" — the two medications work through different mechanisms. Wegovy is a single GLP-1 agonist, while Mounjaro activates both GIP and GLP-1 pathways, which is why starting and maintenance doses differ. Your prescriber will choose based on your medical history.
How long does the titration (dose escalation) take for each medication?
Wegovy titration takes approximately 16 weeks to reach the maximum 2.4 mg dose. Mounjaro titration takes approximately 20 weeks to reach the maximum 15 mg dose. You must spend at least 4 weeks on each dose before increasing. This gradual approach helps your body adjust and allows your prescriber to monitor side effects.
What is the Mounjaro UK prescription process?
Mounjaro (tirzepatide) is prescription-only in the UK. Access through NHS is via referral to a specialist tier 3 weight management service, though availability varies by region. Private access is available through online prescribers following a clinical assessment. Your GP can refer you to NHS services or advise about private options.
Do both Wegovy and Mounjaro require a clinical assessment?
Yes, both are prescription-only medications requiring assessment by a UK-licensed prescriber. A prescriber will review your BMI, health history, current medications, and eligibility before issuing a prescription. Eligibility typically requires BMI ≥30 (or ≥27 with weight-related health conditions). You cannot obtain either medication without this assessment.
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.