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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How Long Does It Take To Lose 5 Stone On Mounjaro?
Losing 5 stone (70 lbs or approximately 32 kg) on Mounjaro depends on several factors including your starting weight, dose, lifestyle changes, and individual metabolism. Clinical trials show that Mounjaro users may achieve significant weight loss over 12–24 months when combined with a reduced-calorie diet and increased physical activity. There is no fixed timeline — results vary considerably between individuals. Your GP or prescriber can give you a personalised estimate based on your specific situation and health goals.
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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.
What Clinical Data Shows About Mounjaro Weight Loss
In the SURMOUNT-1 clinical trial, participants taking Mounjaro (tirzepatide) at the maximum 15 mg dose achieved an average weight loss of approximately 20.9% of their body weight over 72 weeks (approximately 18 months). For a person starting at 120 kg (approximately 18 stone 12 lbs), this would represent around 25 kg (3 stone 13 lbs) of weight loss.
To lose specifically 5 stone (32 kg), the timeline depends heavily on your starting weight:
- Starting at 110 kg (17 stone 4 lbs): Losing 5 stone (32 kg) represents approximately clinically studied weight loss — typically 18–24 months on maximum dose
- Starting at 90 kg (14 stone 2 lbs): Losing 5 stone represents clinically studied weight loss — typically 20–28 months or longer
- Starting at 130 kg (20 stone 7 lbs): Losing 5 stone represents clinically studied weight loss — typically 12–20 months
Important: These are estimates based on clinical trial averages. Individual timelines vary significantly depending on how well you respond to the medication, your adherence to dose titration, and lifestyle changes alongside treatment.
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.
Dose Progression And Timeline Expectations
Mounjaro requires gradual dose titration — you cannot start at the maximum 15 mg dose immediately. The standard escalation takes approximately 20 weeks to reach full dose, meaning weight loss typically accelerates over the first 5–6 months as you reach therapeutic doses.
Weight loss on Mounjaro tends to follow this pattern: slower initial loss (weeks 1–12), moderate loss during dose escalation (weeks 12–20), and more significant loss at maintenance doses (from week 20 onwards). Most users see meaningful weight loss results by 4–6 months, though the majority of clinical trial weight loss occurred between months 6–18. Try our free GLP-1 weight loss calculator to estimate potential results based on your starting weight and projected timeline with dose progression.
- 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.
Will I definitely lose 5 stone on Mounjaro?
No. Mounjaro may help with weight loss, but results vary significantly between individuals. Clinical trials show average weight loss of 15–21%, but some people lose more and some less. Your GP should discuss realistic expectations based on your health profile.
How does Mounjaro's dose titration affect how quickly I lose weight?
Mounjaro requires gradual dose escalation from 2.5 mg to a maximum of 15 mg over approximately 20 weeks. You typically won't see maximum weight loss benefits until reaching therapeutic doses around weeks 16–20. This extended titration period means results build gradually rather than rapidly.
What's the difference between Mounjaro and Wegovy for weight loss timelines?
Both are once-weekly injections but use different mechanisms. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist showing slightly higher average weight loss (~21%) than Wegovy (semaglutide), a GLP-1 agonist only (~15%). Timelines are similar, typically 12–24 months for significant loss.
Can I lose 5 stone faster by skipping doses or increasing Mounjaro faster?
No. Faster dose escalation increases side effects without accelerating weight loss and may be unsafe. Mounjaro must be titrated gradually under prescriber supervision. Weight loss happens through the medication working with lifestyle changes, not through dose rushing.
What should I do if I'm not losing weight after 6 months on maximum Mounjaro dose?
Discuss this with your prescriber. Non-response can be due to lifestyle factors, medications interfering with absorption, or individual variation in response. Your GP may suggest diet review, investigation of underlying health conditions, or alternative approaches rather than continuing indefinitely.
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.