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
Which Mounjaro Dose Is Most Effective?
There is no single "most effective" Mounjaro dose — the right dose depends on your individual health, response to treatment, and tolerance of side effects. Mounjaro (tirzepatide) is a prescription-only injection that starts at 2.5 mg and increases gradually over weeks to a maximum of 15 mg. Clinical trials showed that higher doses produced greater average weight loss, but effectiveness varies significantly between individuals. Your prescriber will work with you to find the dose that balances effectiveness with side effect management.
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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.
How Mounjaro Dosing Works in the UK
Mounjaro is supplied as a once-weekly KwikPen injection. Each pen contains 4 doses (a 4-week supply). The standard UK titration schedule increases your dose every 4 weeks:
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
You must stay on each dose for at least 4 weeks before increasing. This gradual titration allows your body to adjust and helps minimise nausea and other side effects. Your prescriber may pause escalation or keep you on a lower maintenance dose if you are experiencing good results or manageable side effects.
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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 the Clinical Data Shows About Effectiveness
The SURMOUNT-1 clinical trial, conducted over 72 weeks, showed average weight loss increased with higher doses:
- 5 mg dose: approximately clinically studied weight loss
- 10 mg dose: approximately clinically studied weight loss
- 15 mg dose: approximately clinically studied weight loss
However, individual results vary considerably. Some people achieve significant results at 5 mg or 10 mg and choose not to escalate further. Others reach 15 mg and see modest additional benefit. Use our GLP-1 weight loss calculator to project potential outcomes at different doses based on your current weight.
- 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 need to reach the maximum 15 mg Mounjaro dose?
No. Many people achieve their weight loss goals at lower doses like 5 mg or 10 mg. Your prescriber will assess your progress at each dose level and may recommend staying at a maintenance dose rather than continuing to escalate. The "most effective" dose for you is the one that delivers results you are happy with while managing side effects well.
What if I have side effects at a higher Mounjaro dose?
Tell your prescriber immediately. You may pause escalation, stay at your current dose, or reduce to a previously tolerated dose. Nausea, diarrhoea, and constipation are common at higher doses but often improve with time. Dose adjustment is normal and does not mean the medication will not work for you.
How long does it take to see weight loss results on Mounjaro?
Most people notice changes within the first 4–8 weeks, though weight loss is often gradual. The full effect of each dose may take several weeks. Significant weight loss typically becomes evident after 12–16 weeks of treatment. Consistency with diet and physical activity alongside the injection is essential for best results.
Can my GP prescribe Mounjaro, or do I need a specialist?
In the UK, Mounjaro is typically prescribed through specialist tier 3 weight management services following NHS referral, or through private prescribing services following an online clinical assessment. Access and eligibility vary by region. Your GP can discuss referral options or direct you to private providers.
Is tirzepatide (Mounjaro) more effective than other weight loss injections like Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro produced slightly higher average weight loss than Wegovy, but direct comparison is complex. Individual response varies. Your prescriber will recommend based on your health profile and availability. Both are prescription-only and require clinical assessment.
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.