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 Golden Dose Syringe vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they work in different ways. Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it activates two hormone pathways — while Wegovy is a GLP-1 agonist only. The "golden dose" term sometimes refers to maintenance doses in clinical trials, but what matters most is which medication your prescriber determines is suitable for you following a clinical assessment. Understanding the key differences helps you have an informed conversation with your GP or licensed prescriber.
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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.
Clinical Trial Data and Mechanism Differences
The primary difference between Mounjaro and Wegovy lies in their mechanisms. Mounjaro (tirzepatide) activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptor pathways, providing dual hormone signalling. Wegovy (semaglutide) activates GLP-1 receptors only. In the SURMOUNT-1 clinical trial, Mounjaro at 15 mg (maximum dose) showed average weight loss of approximately 20.9% of body weight over 72 weeks. In the STEP-1 trial, Wegovy at 2.4 mg (maximum dose) showed average weight loss of approximately 14.9% over 68 weeks. Both trials included participants following a reduced-calorie diet and increased physical activity. Individual results vary significantly — these are trial averages, not assured outcomes. Your prescriber will assess which medication aligns with your personal health profile and goals.
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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.
Dosing, Timing, and Personal Suitability
Mounjaro starts at 2.5 mg weekly, escalating over weeks to a maximum of 15 mg. Wegovy starts at 0.25 mg weekly, escalating to 2.4 mg maximum. Both are once-weekly injections delivered via pre-filled KwikPen devices. Mounjaro uses the Mounjaro KwikPen, while Wegovy has its own pen. Neither is inherently "better" — suitability depends on your individual health history, any weight-related conditions, previous medication responses, and your prescriber's clinical judgement. Use our free GLP-1 weight loss calculator to see projected outcomes at different doses, and our BMI calculator to understand your current health context. Your GP or licensed prescriber will determine which is appropriate for you.
- 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 in the context of Mounjaro and Wegovy?
"Golden dose" is informal terminology sometimes used to describe the maintenance dose at which trial participants achieved optimal results. For Mounjaro, this is typically 15 mg weekly; for Wegovy, 2.4 mg weekly. However, the optimal dose for any individual varies — your prescriber will titrate you to the dose that works best for your body.
Is Mounjaro more effective than Wegovy?
Clinical trials show different average outcomes, but "more effective" depends on the individual. SURMOUNT-1 showed higher average weight loss with Mounjaro, but individual results vary widely. Effectiveness also depends on adherence, diet, activity level, and personal metabolism. Your prescriber will assess which is more suitable for you.
Why does Mounjaro work differently if both are weight loss injections?
Mounjaro is a dual GIP and GLP-1 agonist, activating two hormone pathways. Wegovy activates GLP-1 only. The dual mechanism in Mounjaro may provide additional appetite regulation and metabolic effects, but this doesn't assures better outcomes for every person.
Can I switch from Wegovy to Mounjaro or vice versa?
Yes, switching is possible and is sometimes done if one medication isn't providing expected results or causes intolerable side effects. However, any switch must be managed by your prescriber — there's no standard conversion chart. Your GP or licensed prescriber will guide the transition safely.
How do I know which medication is right for me?
Your prescriber will assess your medical history, current weight, BMI, any weight-related health conditions, previous medication responses, and personal goals. Both require a prescription and clinical assessment. Neither is available over-the-counter, and both work best alongside a reduced-calorie diet and increased physical activity.
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.