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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Does Mounjaro Boost Metabolism?
Mounjaro doesn't directly "boost" metabolism in the traditional sense, but it works differently than Wegovy. Both are prescription-only weight loss medications available in the UK, but they use different mechanisms to help support weight management. Understanding how each medication affects your body can help you and your GP decide which might be more suitable for you. Let's explore the key differences between tirzepatide (Mounjaro) and semaglutide (Wegovy) in how they work.
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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.
How Mounjaro and Wegovy Work — The Key Difference
Neither Mounjaro nor Wegovy directly increases your metabolic rate, but they support weight loss through appetite and hunger regulation. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two separate hormone pathways in your body. Wegovy (semaglutide) is a GLP-1 agonist only — it activates a single pathway. This dual action in Mounjaro may help regulate appetite, reduce cravings, and support satiety (feeling fuller) in different ways than Wegovy alone.
Both medications also slow gastric emptying — how quickly food leaves your stomach — which contributes to prolonged fullness. Neither directly speeds up calorie burning. In clinical trials, both showed meaningful weight loss results alongside reduced-calorie diet and increased physical activity. Your prescriber will assess which mechanism suits your individual health needs.
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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.
Clinical Trial Results — SURMOUNT vs STEP Data
The SURMOUNT-1 trial showed Mounjaro helped participants lose approximately 20.9% of body weight at the maximum 15mg dose over 72 weeks. The STEP-1 trial showed Wegovy helped participants lose approximately 14.9% of body weight at 2.4mg over 68 weeks. These are average results — individual outcomes vary significantly. Both studies combined medication with a reduced-calorie diet and exercise programme. Try our free GLP-1 weight loss calculator to estimate potential results at different doses, though your actual weight loss depends on many personal factors including diet, activity level, and individual response to medication.
Choosing between Mounjaro and Wegovy is a prescriber decision based on your individual health profile, not just which one might theoretically produce faster results. Both are prescription-only medications requiring a clinical assessment before prescription. Your GP or licensed prescriber will consider your medical history, current medications, weight-related health conditions, and eligibility under NHS NICE guidance or private prescription criteria. Some people respond better to the dual GIP+GLP-1 action of Mounjaro, whilst others do equally well on the single GLP-1 action of Wegovy. Individual suitability cannot be predicted in advance — it's assessed on a case-by-case basis.
- 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.
Does Mounjaro increase your metabolic rate directly?
No. Mounjaro doesn't speed up your metabolism. Instead, it regulates appetite and hunger hormones, helping you eat less and feel fuller. Weight loss occurs primarily through consuming fewer calories, not burning more. Both Mounjaro and Wegovy work this way — through appetite regulation rather than metabolic acceleration.
Why does Mounjaro have a dual mechanism if Wegovy is just GLP-1?
The dual GIP+GLP-1 action in Mounjaro may provide additional appetite regulation and satiety benefits beyond GLP-1 alone. SURMOUNT trial data showed slightly higher average weight loss with Mounjaro compared to Wegovy trials, though results vary individually. Your prescriber will decide which mechanism is more suitable for you.
Is Mounjaro faster for weight loss than Wegovy?
Clinical trial averages showed Mounjaro slightly higher weight loss (approximately 20.9% vs 14.9%), but this doesn't mean it's "faster" for everyone. Individual responses vary significantly. Your actual weight loss depends on diet adherence, physical activity, personal metabolism, and how your body responds to the medication.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is approved by NICE for NHS prescription through specialist tier 3 weight management services, but availability and waiting times vary by region. Private prescription is also available following an online clinical assessment. Your GP can discuss both routes with you.
Do I need to exercise and diet with Mounjaro for it to work?
Yes. Both clinical trials showed Mounjaro and Wegovy work best alongside a reduced-calorie diet and increased physical activity. These medications support weight loss but don't replace lifestyle changes. Use our progress tracker to monitor both weight and healthy habit changes alongside treatment.
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.