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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Tirzepatide Dosing vs Wegovy — How They Compare
Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are prescription-only weight loss injections available in the UK, but their dosing schedules and mechanisms differ significantly. Tirzepatide is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 receptor agonist only. Understanding the differences between tirzepatide dosing and Wegovy can help you understand what a prescriber might recommend based on your individual health needs. Both require a clinical assessment before prescription. Our GLP-1 weight loss calculator can help you 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.
Tirzepatide vs Wegovy — Dosing Schedules and Mechanisms
Tirzepatide (Mounjaro) starts at 2.5 mg weekly and escalates every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg as the maximum dose. Each dose is injected once weekly using a KwikPen device.
Wegovy (semaglutide) uses a gentler escalation schedule, starting at 0.25 mg weekly and progressing through 0.5 mg, 1 mg, 1.7 mg, and reaching a maximum of 2.4 mg weekly.
The key difference lies in their mechanism: tirzepatide activates both GIP and GLP-1 receptors, whilst Wegovy activates GLP-1 receptors only. In clinical trials, SURMOUNT data showed tirzepatide achieved approximately 15–21% average body weight loss, whilst STEP trial data showed Wegovy achieved approximately 15% average body weight loss. However, individual results vary significantly, and both are used alongside reduced-calorie diet and increased physical activity.
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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.
Which Dosing Schedule Is Right for You?
Neither tirzepatide nor Wegovy can be purchased over-the-counter — both are prescription-only medicines requiring a clinical assessment by a UK-licensed prescriber. Your prescriber will evaluate your BMI, weight-related health conditions, medical history, and current medications to determine which weekly weight loss injection, if any, is appropriate for you.
Some people may find tirzepatide's higher maximum dose (15 mg) offers greater flexibility, whilst others may prefer Wegovy's slower escalation schedule due to side effect tolerance. The choice is not about which is "better" — it is about which suits your individual health profile. Use our BMI calculator above to check your starting point, then discuss prescription weight loss options with your GP or a licensed prescriber who can recommend the most suitable approach for your circumstances.
- 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 difference between tirzepatide and semaglutide?
Tirzepatide (Mounjaro) is a dual GIP and GLP-1 receptor agonist, activating two hormone pathways. Semaglutide (Wegovy) is a GLP-1 receptor agonist only, activating one pathway. This difference in mechanism may influence how your body responds, which is why prescribers assess suitability individually. Both are UK prescription-only medicines.
Does tirzepatide work faster than Wegovy?
Both tirzepatide and Wegovy show weight loss effects within weeks, though individual timelines vary. Clinical trials suggest tirzepatide may achieve slightly higher average weight loss percentages (15–21% vs 15%), but this does not mean it works "faster" — both require consistent use over several months alongside lifestyle changes for maximum benefit.
Can I switch from Wegovy to tirzepatide?
Yes, some people do switch between GLP-1 medications, but any change must be managed by your prescriber. There is no official conversion chart — approximate equivalences exist (for example, Wegovy 2.4 mg is roughly equivalent to tirzepatide 15 mg), but your prescriber will assess the safest way to transition based on your response and tolerance.
Why does tirzepatide dosing go higher than Wegovy?
Tirzepatide's dual mechanism (GIP + GLP-1) means its maximum effective dose is higher (15 mg) compared to Wegovy's 2.4 mg. The higher number does not automatically mean "stronger" — it reflects the different way the drug works. Both reach their therapeutic endpoint at their respective maximum doses.
How long does it take to reach the maximum tirzepatide dose?
Tirzepatide requires a minimum of 4 weeks at each dose level before escalating, so reaching the maximum 15 mg dose takes approximately 20–24 weeks (5–6 months). Wegovy follows a similar timeline of approximately 17–20 weeks to reach 2.4 mg. Your prescriber may adjust this schedule based on your tolerance and response to each dose.
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.