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
What Mounjaro Results Look Like After 3 Months
After 3 months on Mounjaro (tirzepatide), most people see measurable weight loss results — but the amount varies significantly between individuals. By month 3, most users are still in the dose-titration phase, typically at doses of 5–7.5mg. This guide explains what clinical data shows, what influences your personal results, and why individual responses differ so much. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses based on clinical trial data.
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.
Expected Weight Loss at 3 Months
At 3 months on Mounjaro, most people have lost between 2–6kg (4–13 lbs), though results vary widely depending on the dose you're taking and how consistently you're following a reduced-calorie diet and increased physical activity.
Dose-dependent results at 3 months:
- 5mg dose: average ~2–3% of body weight lost
- 7.5mg dose: average ~4–5% of body weight lost
- 10mg dose: average ~6–8% of body weight lost
These are estimates based on the SURMOUNT clinical trials, where participants followed reduced-calorie diets alongside the medication. Most UK users are still titrating doses at this stage — you may not yet be at your full dose, which means greater weight loss typically comes in months 4–6.
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.
What Influences Your 3-Month Results
Your Mounjaro results at 3 months depend on several factors: your starting weight, current dose level, how strictly you're following dietary changes, your physical activity level, and your individual metabolism. Some people see dramatic results early; others experience slower, steadier progress. Side effects like nausea and reduced appetite often diminish by month 3, which some people find helps them stick with dietary changes more consistently. Compare your progress using our free progress tracker to monitor weekly changes and identify patterns. Always discuss your specific results with your prescriber — they can assess whether dose adjustments might help.
- 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 weight in 3 months on Mounjaro?
Most people do see weight loss within 3 months, but it's not assured. Individual results vary based on dose, diet adherence, activity level, and metabolism. Your prescriber can discuss realistic expectations for your situation.
Is 3 months long enough to know if Mounjaro is working?
Three months gives a useful indication, but many people continue to lose weight months 4–6 as their dose increases toward the maximum 15mg. Weight loss on GLP-1 medications is often progressive rather than immediate.
Can I expect more dramatic results later on Mounjaro?
Yes. At 3 months, most UK users are still titrating doses (typically at 5–7.5mg). The SURMOUNT trials showed larger average weight loss at higher doses and longer timeframes — typically 15–21% at 15mg over 72 weeks.
How does Mounjaro compare to Wegovy at 3 months?
Clinical trials suggest Mounjaro (dual GIP+GLP-1 agonist) may produce slightly larger average weight loss than Wegovy (GLP-1 only), but individual results vary considerably. Both require prescription and clinical assessment.
What should I do if I haven't lost weight after 3 months?
Contact your prescriber. They can review your dose, dietary adherence, activity level, and overall health. Some people need time to respond; others may benefit from dose adjustment or lifestyle review.
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.