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 Weight Loss on Mounjaro Per Week — What to Expect
Mounjaro (tirzepatide) is a prescription-only weight management injection that may help adults lose weight at varying rates. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks — though individual results vary significantly. Understanding expected weekly weight loss, how it relates to your starting BMI, and how it compares to NHS healthy weight guidelines can help you set realistic goals. Weight loss is not assured and depends on your starting weight, lifestyle changes, and individual response to the medication.
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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.
Weekly Weight Loss Rates and BMI Context
Clinical trials of Mounjaro showed that average weekly weight loss typically ranges from 0.5 to 1.5 kg per week during the initial treatment phase, though this varies considerably between individuals. The NHS recommends a sustainable weight loss rate of 0.5 to 1 kg per week for long-term success. On Mounjaro, weight loss tends to be faster in the first 12–16 weeks as doses are increased, then may stabilise or slow as the body adapts.
For someone with a BMI of 30 (obese category), losing 1 kg per week could bring their BMI down by approximately 0.5–0.6 points per week, assuming stable height. The total weight loss depends on your starting weight, your individual health factors, and how consistently you follow the reduced-calorie diet and physical activity guidance alongside the medication. Calculate your personal BMI using our free BMI calculator above to understand your current weight category and healthy weight range.
- Early phase (weeks 1–16): often faster loss as doses escalate
- Maintenance phase (week 17+): weight loss may slow or stabilise
- Variation: individual results range from minimal loss to 2+ kg per week
Clinically BackedWeight Loss
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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.
Relating Weekly Loss to Your Ideal Body Weight
Your ideal body weight range is determined by your height and BMI. For a healthy BMI of 18.5–24.9, you can calculate your target weight range using a height-to-weight formula. For example, an adult who is 5ft 8in (173 cm) tall has a healthy weight range of approximately 55–74 kg (8st 8lbs to 11st 8lbs). If you start at 85 kg with the same height, you would need to lose roughly 11–30 kg to reach the healthy weight range — which at an average rate of 1 kg per week would take 11–30 weeks.
Use the weight converter on this page to check your current weight in stone and kg, then use our GLP-1 weight loss calculator to estimate potential outcomes at different Mounjaro doses. Your GP can also discuss realistic timescales for reaching your ideal weight based on your individual starting point and health goals.
Your ideal body weight range is determined by your height and BMI. For a healthy BMI of 18.5–24.9, you can calculate your target weight range using a height-to-weight formula. For example, an adult who is 5ft 8in (173 cm) tall has a healthy weight range of approximately 55–74 kg (8st 8lbs to 11st 8lbs). If you start at 85 kg with the same height, you would need to lose roughly 11–30 kg to reach the healthy weight range — which at an average rate of 1 kg per week would take 11–30 weeks.
Use the weight converter on this page to check your current weight in stone and kg, then use our GLP-1 weight loss calculator to estimate potential outcomes at different Mounjaro doses. Your GP can also discuss realistic timescales for reaching your ideal weight based on your individual starting point and health goals.
- 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 average weight loss per week on Mounjaro?
Clinical trials showed average weight loss of 0.5 to 1.5 kg per week, though this varies by individual. The NHS recommends losing 0.5 to 1 kg per week as a sustainable rate. Weight loss is typically faster during dose escalation phases and may slow during maintenance phases.
How does weekly weight loss on Mounjaro relate to BMI change?
At a weekly loss of 1 kg, your BMI typically decreases by approximately 0.5–0.6 points per week (assuming stable height). Someone starting at BMI 30 could potentially reach the overweight category (BMI 25) by losing roughly 30–35 kg, depending on their height and individual factors.
How long does it take to reach a healthy weight on Mounjaro?
Time to reach a healthy BMI (18.5–24.9) depends on your starting weight and height. Using our GLP-1 weight loss calculator, you can estimate your timeline based on your personal measurements. Your prescriber can also provide guidance on realistic timescales.
Is 1 kg per week weight loss on Mounjaro safe?
Yes — the NHS considers a loss of 0.5 to 1 kg per week safe and sustainable. Mounjaro may achieve faster loss in early phases, which is generally considered acceptable when combined with proper nutrition and medical oversight. Discuss your individual rate with your GP.
Why does weight loss vary so much between individuals on Mounjaro?
Weight loss depends on starting weight, adherence to diet and exercise, individual metabolism, genetics, medications, and medical conditions. Clinical trials show individual results ranging from minimal loss to 2+ kg per week. Track your personal progress using our free progress tracker.
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.