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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Mounjaro Dosage Amounts in the UK
Mounjaro (tirzepatide) is available in six escalating doses from 2.5 mg to 15 mg, given as a once-weekly injection via a KwikPen device. The NHS approves tirzepatide for weight management in adults meeting specific BMI and health criteria through specialist tier 3 weight management services. Understanding the dosage schedule, how doses are increased, and what each dose contains will help you know what to expect if prescribed. This guide covers the UK prescribing approach, eligibility criteria, and how our free GLP-1 weight loss calculator can help you estimate potential outcomes at different doses.
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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 Dosage Schedule and Escalation in the UK
Mounjaro is prescribed in a stepped dosage titration schedule, meaning you start at a low dose and increase gradually every 4 weeks if tolerated. This approach allows your body to adjust to the medication and reduces side effects.
- 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 onwards: 15 mg once weekly (maximum dose)
Each KwikPen contains 4 weekly doses, so one pen lasts 4 weeks at any given dose level. You must stay on each dose for a minimum of 4 weeks before escalating, even if you feel ready to increase. Your prescriber will assess your progress and tolerability before approving the next dose increase. If you experience significant side effects, your dose may be held at the current level or increased more slowly.
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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, Eligibility, and Expected Outcomes
In the UK, Mounjaro (tirzepatide) is available through NHS specialist tier 3 weight management services for adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds (27.5 kg/m²). NHS access requires a GP referral to a specialist weight management service, and availability varies significantly by region. Clinical trial data (SURMOUNT-1) showed average weight loss of approximately 15–21% of body weight across doses, achieved alongside reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to explore potential outcomes based on your starting weight and target dose.
Private prescribing in the UK offers an alternative route: GPhC-registered online pharmacies can issue prescriptions following a clinical assessment with a UK-licensed prescriber, without needing an NHS referral. This allows faster access but at private cost (typically £129–£320+ per month depending on dose). Whether accessing via NHS specialist services or private prescribing, Mounjaro is always prescription-only and requires clinical assessment. Your prescriber will determine the most appropriate starting and target doses for your individual circumstances. Track your weight loss progress using our free progress tracker as you advance through the dosage schedule.
- 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.
What is the starting dose of Mounjaro in the UK?
The standard starting dose is 2.5 mg, given as a once-weekly injection via a KwikPen. You remain on this dose for 4 weeks before potentially increasing to 5 mg, assuming the medication is well tolerated and your prescriber approves the escalation.
How often are Mounjaro doses increased?
Doses increase every 4 weeks minimum, following the titration schedule. However, if you experience significant side effects or your prescriber has concerns, you may stay on the same dose longer or increase more gradually.
What is the maximum dose of Mounjaro?
The maximum approved dose is 15 mg once weekly. Not all patients need to reach this dose—your prescriber will determine the optimal dose for your weight loss goals and tolerability.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is NICE-approved and available through NHS specialist tier 3 weight management services for eligible adults. Access requires a GP referral and varies by region; waiting times can be lengthy. Private prescribing is also available as an alternative.
How much weight loss should I expect at each Mounjaro dose?
Clinical trials showed an average loss of 15–21% of body weight at maximum dose, but individual results vary significantly. Our GLP-1 weight loss calculator can provide estimated projections based on your starting weight—though your prescriber should always be your primary source for personal expectations.
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.