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 Mounjaro Dosage in the UK?
The highest Mounjaro dosage available in the UK is 15 mg once weekly. This is the maximum therapeutic dose of tirzepatide approved by the MHRA for weight management in British adults. Mounjaro is a prescription-only injection that must be prescribed by a UK-licensed healthcare professional following a clinical assessment. The dose is increased gradually over several months, starting at 2.5 mg, with adjustments every four weeks until the optimal therapeutic dose is reached. Not all patients require the maximum dose — your prescriber will determine the right dose for your individual circumstances.
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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.
UK Mounjaro Dosage Schedule and Titration
Mounjaro dosing follows a structured titration schedule set out by the MHRA and followed by NHS and private prescribers across the UK. Each dose is a once-weekly KwikPen injection, with a minimum of four weeks at each dose level before increasing to the next step.
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first maintenance dose)
- Weeks 9–12: 7.5 mg (optional escalation)
- Weeks 13–16: 10 mg (escalation if needed)
- Weeks 17–20: 12.5 mg (escalation if needed)
- Week 21+: 15 mg (maximum/final dose)
Clinical trials showed that tirzepatide at the highest 15 mg dose produced greater average weight loss compared to lower doses. However, individual results vary significantly, and some patients experience adequate results at lower doses. Your GP or private prescriber will monitor your progress and adjust your dose based on your response and tolerance to the medication. If you experience significant side effects, your dose may be reduced rather than increased.
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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 Access to Mounjaro and Private Prescribing Routes
In the UK, Mounjaro is available through both NHS specialist weight management services (tier 3) and private prescribing. NHS access requires referral to your regional tier 3 weight management service, though availability varies considerably across different integrated care boards (ICBs). Waiting lists for NHS services can be lengthy in many areas. Private access is available through GPhC-registered online pharmacies following a remote clinical assessment with a UK-licensed prescriber — this route allows faster access without NHS referral. Regardless of route, a clinical assessment is mandatory to confirm eligibility based on BMI thresholds and health conditions. Use our free GLP-1 weight loss calculator to estimate potential outcomes, and our BMI calculator to confirm your current health classification before discussing treatment options with a healthcare professional.
- 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 request the 15 mg dose immediately?
No. Mounjaro must be titrated gradually, starting at 2.5 mg with a minimum of four weeks between dose increases. This approach allows your body to adjust and reduces side effects. Rapid escalation to 15 mg is not recommended and would not be prescribed by any UK healthcare provider following MHRA guidance.
What does MHRA approval mean for Mounjaro dosing?
The MHRA (Medicines and Healthcare Products Regulatory Agency) is the UK medicines regulator. MHRA approval confirms that Mounjaro, including the 15 mg maximum dose, has been assessed as safe and effective for weight management in UK adults when prescribed and monitored appropriately by a licensed healthcare professional.
Is the 15 mg dose available through the NHS?
Yes, Mounjaro including the 15 mg dose is available through NHS tier 3 specialist weight management services in most areas, though eligibility and availability vary by region. Access is typically through referral from your GP to your local ICB-commissioned service. Private prescribing is also available without NHS referral.
How long does it take to reach the highest 15 mg dose?
Reaching the maximum 15 mg dose takes approximately 20 weeks (just over four months) from the initial 2.5 mg starting dose, assuming you progress through each dose level without pausing. Some patients may take longer if side effects require staying at a dose for additional weeks.
What if the highest dose doesn't work for me?
If 15 mg Mounjaro doesn't produce the desired weight loss result, your prescriber may consider other options including other GLP-1 medications (such as Wegovy), lifestyle intensification, or referral for tier 4 bariatric surgery assessment. Individual response to weight loss medications varies significantly. Try our GLP-1 calculator to explore projected outcomes at different doses.
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.