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 Is the Highest Mounjaro Dosage in the UK?
The highest Mounjaro dosage available in the UK is 15 mg once weekly. This maximum dose is reached gradually through a structured titration schedule — you don't start at 15 mg. Instead, your prescriber will increase your dose every 4 weeks, starting at 2.5 mg, to monitor how your body responds and manage side effects effectively. Most people achieve good results at lower doses, and reaching the maximum isn't necessary for everyone.
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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.
Mounjaro Dose Titration Schedule in the UK
Mounjaro dosing follows a careful step-by-step approach, with each dose lasting exactly 4 weeks before any increase. This is called dose titration and helps your body adjust while minimising side effects like nausea and stomach discomfort.
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly
- Weeks 9–12: 7.5 mg once weekly
- Weeks 13–16: 10 mg once weekly
- Weeks 17–20: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum dose)
Your prescriber may pause increases or adjust the schedule based on your response and any side effects. Each KwikPen contains 4 doses, representing a 4-week supply. You won't reach the highest Mounjaro dosage until at least 5 months into treatment — this gradual approach is essential for safety and tolerability.
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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.
Do You Need the Highest Dose for Results?
No — clinical trial data shows that weight loss occurs at all Mounjaro doses, and the highest dose isn't required for everyone. In SURMOUNT trials, the 5 mg dose (the first maintenance level) produced approximately 15% average body weight loss, whilst 15 mg produced around 21%. However, individual results vary significantly, and many people achieve their weight loss goals at 10 mg or 12.5 mg. Your prescriber will assess your progress at each dose level and may recommend staying at a dose where you're seeing good results and tolerating side effects well. Use our GLP-1 weight loss calculator to explore projected outcomes, and remember that results depend on lifestyle changes alongside medication.
- 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.
Can I start at 15 mg Mounjaro straight away?
No. UK prescribers always start at 2.5 mg and increase every 4 weeks. Starting at the highest dose would cause severe side effects and is not clinically recommended. The gradual titration schedule allows your body to adapt safely.
How long does it take to reach 15 mg Mounjaro?
It takes at least 20 weeks (approximately 5 months) to reach the maximum 15 mg dose, assuming no pauses in the titration schedule. Your prescriber may extend this timeline if needed.
Will a higher Mounjaro dose assures more weight loss?
Higher doses are associated with greater average weight loss in clinical trials, but individual results vary. Many people achieve significant results at lower doses. Your prescriber will adjust based on your response and side effects.
Is 15 mg Mounjaro the highest dose available in the UK?
Yes. 15 mg once weekly is the maximum licensed Mounjaro dose in the UK. It is also the highest dose used in clinical trials. Doses above 15 mg are not approved for weight management.
What happens if I can't tolerate higher Mounjaro doses?
If side effects become difficult at a higher dose, your prescriber can keep you on a lower maintenance dose where you tolerate it well. Weight loss still occurs at lower doses — tolerability is more important than reaching the maximum.
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.