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
How Much Weight Can You Lose With Mounjaro?
The amount of weight you can lose with Mounjaro varies significantly between individuals, but clinical trials show an average weight loss of 15–21% of body weight over 72 weeks. However, your personal results depend on many factors including your starting weight, BMI, lifestyle changes, and how your body responds to the medication. To understand what your healthy weight target might be, use our free BMI calculator above to see your current BMI and the healthy weight range for your height. This gives you a personal benchmark for what weight loss with Mounjaro could help you achieve.
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.
Understanding Your Personal Weight Loss Potential With BMI
Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist that works by regulating appetite and supporting feeling fuller after smaller meals. Clinical evidence from the SURMOUNT-1 trial showed average weight losses of approximately 15% at the 5mg dose, 19.5% at 10mg, and 20.9% at the highest 15mg dose—but these are trial averages, not assures.
Your healthy weight range depends on your height and BMI. The NHS defines a healthy BMI as 18.5–24.9, though for people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply (18.5–22.9). Use the BMI calculator on this page to discover your personal healthy weight range. If you're currently overweight or obese (BMI 25 or above), Mounjaro may help you progress toward that target—but weight loss medications work alongside, not instead of, diet and activity changes.
- Average weight loss with Mounjaro: 15–21% of body weight
- Timeline: results typically visible over 12–24 weeks
- Individual variation: some lose more, some less—genetics, metabolism, and adherence all matter
- Requires reduced-calorie diet and physical activity for best results
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.
What to Do If Your Current Weight Is Above the Healthy Range
If the BMI calculator shows your weight is above the healthy range for your height, the first step is to discuss your options with your GP. They can assess whether prescription weight loss medication like Mounjaro is appropriate for you—eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure.
Start by understanding your targets: work backwards from your healthy weight range to set realistic, incremental goals. Losing even 5–10% of your body weight (achievable with or without medication) can deliver significant health improvements: better blood sugar control, lower blood pressure, reduced joint pain, and improved energy. Our free progress tracker helps you log weight changes week-to-week and stay motivated. Your GP or a prescriber can then assess whether Mounjaro or another treatment fits your individual circumstances.
- 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's the difference between average weight loss in trials and what I might lose?
Clinical trial averages (15–21% with Mounjaro) represent typical results in controlled settings with diet and exercise support. Your individual loss depends on your starting weight, metabolism, adherence, diet quality, activity level, and genetics. Some people lose more, some less. Always discuss realistic expectations with your prescriber.
How quickly will I see weight loss results with Mounjaro?
Most people begin to notice changes within 4–8 weeks, but significant weight loss typically takes 12–24 weeks. Mounjaro is dosed gradually over weeks 1–20, so your body is adjusting throughout. Patience and consistent lifestyle changes are essential—rapid loss isn't the goal; sustainable loss is.
Can I use the BMI calculator to find my target weight?
Yes. The BMI calculator on this page shows your current BMI and the healthy weight range for your height according to NHS guidelines. Use the lower and upper bounds of the healthy range (BMI 18.5–24.9) as your targets. For South Asian, Chinese, or Black African/Caribbean adults, lower thresholds apply—your GP can advise your personal goal.
Do I need to change my diet and exercise if I take Mounjaro?
Yes. Mounjaro is most effective alongside a reduced-calorie diet and regular physical activity. The medication helps reduce appetite and cravings, but it's not a replacement for lifestyle changes. Clinical trials that showed the best results combined Mounjaro with diet and exercise support.
Is Mounjaro available on the NHS for weight loss?
NICE has approved tirzepatide (Mounjaro) for NHS use, but access varies significantly by region. You typically need referral to a specialist tier 3 weight management service through your GP. Private prescribing is also available following an online clinical assessment. Discuss both options with your GP. ```
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.