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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Mounjaro and Wegovy Doses: How They Compare
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections licensed in the UK, but they use different dosing schedules and mechanisms. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy activates only the GLP-1 pathway. Understanding their dose ranges, titration schedules, and expected outcomes can help you and your prescriber determine which might be more suitable for your individual health needs. This guide compares both medications side-by-side.
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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 and Starting Doses
Mounjaro (tirzepatide) starts at 2.5 mg once weekly and escalates every 4 weeks through 5 mg, 7.5 mg, 10 mg, 12.5 mg, reaching a maximum of 15 mg once weekly. Each KwikPen contains 4 doses (a 4-week supply). Wegovy (semaglutide) uses a slower titration beginning at 0.25 mg weekly, escalating through 0.5 mg, 1 mg, and 1.7 mg, with a maximum dose of 2.4 mg once weekly. Wegovy's lower starting dose reflects its single GLP-1 mechanism compared to Mounjaro's dual pathway.
- Mounjaro: minimum 4 weeks between dose increases
- Wegovy: escalation typically over 16–20 weeks to reach 2.4 mg
- Both are once-weekly injections administered by the user at home
- Both use pre-filled auto-injection pens for ease of use
Your prescriber will adjust your dose based on your tolerance and response. The UK prescription pathway requires a clinical assessment before initiation and ongoing monitoring during treatment.
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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.
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Clinical Trial Results and Individual Suitability
In the SURMOUNT-1 trial, Mounjaro at 15 mg achieved average weight loss of approximately 21% body weight over 72 weeks. Wegovy's STEP-1 trial showed average weight loss of approximately 15% body weight at 2.4 mg over 68 weeks—both alongside reduced-calorie diet and physical activity. However, individual results vary significantly, and some people may achieve meaningful weight loss at lower doses. Neither medication assures a specific weight loss outcome. Your GP or prescriber will assess your eligibility based on your BMI, health conditions, and personal circumstances. Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses.
- 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 main difference between Mounjaro and Wegovy doses?
Mounjaro is a dual GIP/GLP-1 agonist starting at 2.5 mg and reaching 15 mg maximum weekly. Wegovy is GLP-1-only, starting at 0.25 mg and reaching 2.4 mg maximum weekly. Mounjaro's higher doses reflect its dual mechanism; Wegovy's lower doses are proportional to its single pathway activation.
How long does it take to reach the maximum dose on each medication?
Mounjaro typically reaches maximum dose (15 mg) in approximately 20–24 weeks with 4-week intervals between increases. Wegovy takes approximately 16–20 weeks to reach 2.4 mg with weekly escalations. Your prescriber may adjust timelines based on your individual tolerance and response.
Which medication causes greater weight loss in clinical trials?
SURMOUNT trial data showed Mounjaro at 15 mg resulted in approximately 21% average body weight loss, while STEP trial data showed Wegovy at 2.4 mg resulted in approximately 15% average weight loss. However, individual outcomes vary considerably, and some people respond better to one medication than the other.
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications requires prescriber guidance—there is no official conversion chart, though approximate equivalences exist (5 mg Mounjaro ≈ 0.5 mg Wegovy, 15 mg Mounjaro ≈ 2.4 mg Wegovy). Any switch must be managed by your prescriber with appropriate washout and monitoring periods.
How do I know which dose is right for me?
Your prescriber will start you on the lowest dose and titrate upward based on your tolerance, side effects, and weight loss response. Check your personal BMI using our free BMI calculator, then discuss your eligibility and optimal dose with your GP or the prescriber conducting your clinical assessment.
Ready to take control of your weight loss journey?
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