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
Free tracker included with every download this week
Average Weekly Weight Loss on Mounjaro vs Wegovy
Average weekly weight loss on Mounjaro and Wegovy depends on several factors including dose, individual metabolism, and lifestyle changes. Clinical trials show both medications support weight loss, but at different rates. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. This means they work through different mechanisms, which affects how much weight people lose per week. It's important to understand that results vary significantly between individuals, and both are prescription-only medicines requiring clinical assessment before use.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
SURMOUNT vs STEP Trial Data: Weekly Weight Loss Comparison
Clinical trials provide the clearest evidence for weekly weight loss expectations. The SURMOUNT-1 trial for Mounjaro showed participants lost an average of 20.9% of body weight over 72 weeks at the maximum dose of 15mg — equivalent to approximately 0.24kg (5.3lbs) per week on average. The STEP-1 trial for Wegovy showed average weight loss of 14.9% of body weight over 68 weeks at 2.4mg — approximately 0.19kg (4.2lbs) per week on average.
However, weekly loss is not linear. Most people experience rapid initial loss in weeks 1–4, slower loss during dose escalation, and then stabilised loss at maintenance doses. The difference between Mounjaro and Wegovy reflects their different mechanisms: Mounjaro activates both GIP and GLP-1 pathways, whilst Wegovy activates GLP-1 only. This dual mechanism may contribute to Mounjaro's slightly higher average loss, though individual response varies considerably.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Individual Variation and Suitability: Your Results May Differ
Average trial data masks significant individual variation. Some people lose 0.5kg per week, others 0.2kg per week, and some experience weight loss plateaus. Factors affecting your personal weekly loss include: starting weight, age, baseline metabolism, adherence to calorie deficit and physical activity, dose tolerance, and genetic factors.
Neither medication is "better" — suitability depends on individual health, previous medication responses, and prescriber assessment. Your GP or a licensed prescriber will assess which is appropriate for you. Both require a uk prescription and clinical assessment. Try our free GLP-1 weight loss calculator above to estimate potential outcomes based on your individual circumstances, or use the progress tracker to monitor your actual weekly loss once you begin 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.
How much weight do most people lose per week on Mounjaro?
Clinical trial data shows average weekly loss of approximately 0.24kg (5.3lbs) per week at maximum dose, but this varies significantly. Some people lose more, others less. Weekly loss is fastest in the first 4 weeks and typically slows over time. Individual factors like diet, exercise, starting weight, and metabolism affect your personal rate.
Is Mounjaro faster for weekly weight loss than Wegovy?
On average, yes — trial data shows Mounjaro achieved slightly higher weekly loss (0.24kg vs 0.19kg per week). However, this is an average across hundreds of participants. Individual variation is substantial, and some Wegovy users lose more per week than some Mounjaro users. Your personal result depends on many individual factors, not the medication alone.
Why do people lose weight differently each week on these injections?
Weekly loss varies because weight loss is not linear. Initial weeks often show rapid loss due to fluid changes and calorie deficit. As you progress, loss typically slows as your body adapts. Weight naturally fluctuates day-to-day due to water retention, hormones, and digestion. This is normal and doesn't mean the medication isn't working.
Can I achieve the trial average weight loss of 20% on Mounjaro?
Trial participants achieved 20.9% average loss by combining the medication with a reduced-calorie diet and increased physical activity. Your individual result depends on adherence to these lifestyle changes, dose escalation tolerance, and personal metabolism. Many people achieve significant loss; some exceed trial averages, others see more modest results.
How do I track my weekly weight loss progress on Mounjaro or Wegovy?
Weighing weekly (same day, same time) helps identify trends over 4-week cycles rather than daily fluctuation. Our free progress tracker on this page lets you log weekly measurements and see your trend over time. Remember: weight loss is not always linear, and weight loss injection therapy works best when combined with sustained dietary changes and 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.