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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What Is the Highest Dose of Mounjaro in the UK?
The highest dose of Mounjaro (tirzepatide) licensed for weight management in the UK is 15 mg once weekly. This maximum dose is reached gradually through a dose titration schedule, starting at 2.5 mg and increasing every 4 weeks. Not all patients require or will reach the highest dose—your GP or prescriber will assess what's appropriate for you based on your individual health, response to the medication, and any side effects. Understanding the dosing pathway helps you know what to expect if prescribed Mounjaro for weight management in the UK.
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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.
Mounjaro Dosing Schedule and Maximum Dose in the UK
Mounjaro is supplied in a pre-filled KwikPen device, with each pen containing four weekly doses. The UK dosing schedule follows this progression:
- Weeks 1–4: 2.5 mg once weekly (starting/adjustment dose)
- Weeks 5–8: 5 mg once weekly (first maintenance)
- Weeks 9–12: 7.5 mg once weekly (escalation if tolerated)
- Weeks 13–16: 10 mg once weekly (escalation if needed)
- Weeks 17–20: 12.5 mg once weekly (escalation if needed)
- Week 21 onwards: 15 mg once weekly (maximum dose)
Each dose increase occurs after a minimum of 4 weeks on the previous dose. Your prescriber will not automatically increase your dose—they will assess your tolerance, side effects, and weight loss response. Some patients remain on 5 mg or 10 mg and achieve good results without reaching the highest dose. The MHRA-approved product information and NICE guidance support this individualised approach.
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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.
NHS Prescribing and Private Access for Mounjaro in the UK
NHS access to Mounjaro is through specialist tier 3 weight management services following GP referral. NICE has approved tirzepatide for NHS use, but availability varies significantly by region and ICB (Integrated Care Board). Waiting lists can be substantial in many areas. Private prescribing is available through UK-licensed prescribers accessed via online consultation with a GPhC-registered pharmacy—you do not need an NHS referral this way. Whether NHS or private, your prescriber will assess your BMI, weight-related health conditions, and medical history before issuing a prescription. Both routes require clinical assessment; Mounjaro is prescription-only and cannot be obtained without this evaluation.
- 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 reach 15 mg Mounjaro if I start at 2.5 mg?
Yes. If you tolerate each dose and your prescriber assesses that dose escalation is appropriate, you can progress from 2.5 mg to 15 mg over approximately 20 weeks. However, many patients achieve their weight loss goals at lower doses (5 mg, 10 mg, or 12.5 mg) and do not need the maximum dose. Your prescriber will individualise your dosing based on your response and any side effects.
What's the difference between Mounjaro and Wegovy dosing?
Mounjaro (tirzepatide) reaches a maximum of 15 mg once weekly, whilst Wegovy (semaglutide) reaches a maximum of 2.4 mg once weekly. Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. The dose numbers cannot be directly compared—they work through different mechanisms.
How long does it take to reach the highest Mounjaro dose?
Approximately 20–21 weeks if you escalate every 4 weeks without delay. If your prescriber recommends staying at a lower dose or pausing escalations due to side effects, it may take longer. Some patients never escalate beyond 10 mg if they achieve good results and tolerability at that dose.
What if I cannot tolerate higher doses of Mounjaro?
If you experience bothersome side effects at a particular dose, your prescriber may recommend staying at that dose long-term or reducing to a previous dose. Weight loss injections are personalised—there is no obligation to reach 15 mg. Discuss any concerns with your GP or prescriber immediately.
Is the 15 mg dose assured to give better results than 10 mg?
No. Clinical trial data showed slightly higher average weight loss at 15 mg than at lower doses, but individual results vary considerably. Some patients achieve excellent weight loss results at 5 mg or 10 mg. Your prescriber will work with you to find the dose that balances efficacy with tolerability for your situation.
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.