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 vs Wegovy: How Prescribers Find Your Optimal Dose
The term "golden dose" refers to the point where you achieve meaningful weight loss with manageable side effects — but this dose is different for every person. When comparing Mounjaro (tirzepatide) and Wegovy (semaglutide), both use gradual dose titration to help your body adjust, but they follow different escalation schedules and mechanisms. Understanding how prescribers determine your optimal dose — and how the two medications compare — can help you have an informed conversation with your GP or licensed prescriber about which might suit you best.
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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.
How Mounjaro and Wegovy Dosing Differ: Mechanism, Titration, and Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two appetite and satiety pathways simultaneously. It starts at 2.5 mg weekly and escalates in 2.5 mg increments every 4 weeks, reaching a maximum of 15 mg weekly. In the SURMOUNT clinical trials, the average weight loss at maximum dose (15 mg) was approximately 20.9% of body weight over 72 weeks.
Wegovy (semaglutide) is a GLP-1-only agonist, starting at 0.25 mg weekly and escalating more gradually — 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and finally 2.4 mg at week 17 onwards. In STEP trials, the average weight loss at the maximum dose (2.4 mg) was approximately 14.9% of body weight over 68 weeks. The slower, lower-dose escalation in Wegovy may suit those who experience side effects more readily.
- Mounjaro: faster titration, higher maximum dose, dual mechanism
- Wegovy: slower titration, lower maximum dose, single GLP-1 mechanism
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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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Finding Your "Golden Dose": Individual Assessment, Not One-Size-Fits-All
Your prescriber will not automatically push you to the maximum dose. The "golden dose" is the dose where you experience meaningful weight loss whilst keeping side effects tolerable and your health stable. Some people achieve this at mid-range doses — for example, 10 mg Mounjaro or 1.7 mg Wegovy — whilst others may reach maximum dose or even step back down if side effects become problematic.
Both medications require a clinical assessment before prescription. Your prescriber will review your medical history, current medications, BMI, and weight-related health conditions to recommend a starting point. You can use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, but your prescriber's individualised assessment is what determines your actual prescription. Your GP or licensed prescriber will monitor your response every 4 weeks and adjust your dose accordingly.
- 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 does "golden dose" mean with Mounjaro or Wegovy?
The golden dose is the dose where you achieve meaningful weight loss with side effects you can manage. It's individual — not necessarily the maximum dose. Your prescriber will help you find it through gradual titration and regular monitoring.
Does Mounjaro reach therapeutic dose faster than Wegovy?
Yes. Mounjaro reaches its maximum (15 mg) by week 21 with 2.5 mg increments every 4 weeks. Wegovy reaches maximum (2.4 mg) by week 17 but with smaller dose increments. Mounjaro's faster titration may suit some; Wegovy's slower approach may suit those sensitive to side effects.
Can I stay on a lower dose of Mounjaro or Wegovy instead of going to maximum?
Absolutely. Many people stabilise on mid-range doses and experience significant weight loss without pushing to maximum. Your prescriber will discuss what dose feels right for your health, weight loss goals, and side effect tolerance.
How do I know if my dose is working?
Your prescriber will assess weight loss, blood sugar control (if diabetic), side effects, and overall health every 4 weeks. If weight loss has plateaued or side effects are unmanageable, your dose may be adjusted. Keep a progress tracker to monitor your weight changes between appointments.
Which medication — Mounjaro or Wegovy — is more likely to help me reach my goal weight?
Both are effective, but individual response varies. Mounjaro showed slightly higher average weight loss in trials (20.9% vs 14.9%), but this doesn't predict your personal outcome. Your prescriber will recommend based on your medical history, medications, and suitability. A licensed prescriber's clinical assessment is essential.
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.