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 Dosage Levels vs Wegovy: UK Comparison
Mounjaro and Wegovy are both prescription-only weight management injections available in the UK, but they work differently and have different dosage schedules. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only medication. Understanding the dosage differences, how each is titrated, and what the clinical trial data showed can help you and your GP or prescriber discuss which option might be more suitable for your individual health needs. Both require a 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.
Mounjaro vs Wegovy Dosage: Key Differences
Mounjaro dosage schedule: Starts at 2.5 mg once weekly for weeks 1–4, then escalates by 2.5 mg increments every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg as the maximum maintenance dose. Each KwikPen contains 4 weeks of doses.
Wegovy dosage schedule: Begins at 0.25 mg once weekly for weeks 1–4, escalating to 0.5 mg, 1 mg, 1.7 mg, and finally 2.4 mg as the maximum dose. The escalation is more gradual and takes longer overall.
- Mounjaro: 2.5 mg → 15 mg (six dose levels, ~5 mg jumps)
- Wegovy: 0.25 mg → 2.4 mg (five dose levels, variable jumps)
- Both are once-weekly injections
- Both require minimum 4 weeks at each dose before escalation
In SURMOUNT-1 clinical trials, Mounjaro at 15 mg showed average weight loss of approximately 20.9% of body weight over 72 weeks. Wegovy showed approximately clinically studied weight loss at 2.4 mg in STEP-1 trials. However, individual results vary significantly, and these are clinical trial averages achieved alongside diet and exercise changes.
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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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Which Dosage Level Is Right for You?
The dosage your prescriber recommends depends on your individual health profile, how well you tolerate the medication at each level, and your weight loss response. Some people reach their target weight at lower doses (e.g., Mounjaro 10 mg or Wegovy 1.7 mg), whilst others continue escalating to the maximum. Prescribers typically start at the lowest dose to allow your body to adjust, then gradually increase if tolerated.
Suitability factors: Both medications require a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. The dual mechanism of Mounjaro (GIP + GLP-1) may suit some people better than Wegovy's single GLP-1 pathway, but this is an individual prescriber decision. Your GP can assess your personal circumstances and help determine the best option. Use our free GLP-1 weight loss calculator to project potential outcomes, and track progress with our progress tracker once you start treatment.
- 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 starting dose for Mounjaro vs Wegovy?
Mounjaro starts at 2.5 mg once weekly, whilst Wegovy starts at 0.25 mg once weekly. Mounjaro's starting dose is higher in absolute terms, but both are designed as gentle introduction doses. Each medication escalates at its own pace — Mounjaro reaches its maximum (15 mg) faster than Wegovy (2.4 mg).
Can I stay on a lower Mounjaro or Wegovy dose if it's working?
Yes. If you achieve good weight loss and feel stable on, for example, Mounjaro 10 mg or Wegovy 1.7 mg, your prescriber may keep you at that dose rather than escalating further. The goal is sustained weight loss and tolerability, not necessarily reaching the maximum dose.
How long does it take to reach the maximum Mounjaro dosage?
Mounjaro takes approximately 20–24 weeks (roughly 5–6 months) to reach the maximum 15 mg dose if escalating every 4 weeks without pausing. Wegovy takes longer, approximately 24–28 weeks, due to its smaller dose increments.
Is Mounjaro more effective than Wegovy because of higher dosages?
SURMOUNT-1 trial data showed Mounjaro achieved slightly higher average weight loss than Wegovy's STEP-1 trials, but results vary individually. The dual GIP + GLP-1 mechanism of Mounjaro may contribute to outcomes, but individual response depends on metabolism, lifestyle, and other health factors. Both require clinical assessment to determine suitability.
Can I switch between Mounjaro and Wegovy if I don't tolerate one?
Switching between medications requires prescriber guidance. Approximate dose equivalences exist (Mounjaro 5 mg ≈ Wegovy 0.5 mg; 10 mg ≈ 1.7 mg; 15 mg ≈ 2.4 mg), but any switch must be managed individually. Discuss concerns with your GP or the prescriber managing your care.
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