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 Doses — Complete UK Guide
Mounjaro (tirzepatide) is a prescription-only, once-weekly injection for weight management in UK adults. The medication comes in six dose strengths, starting at 2.5 mg and escalating up to 15 mg maximum. Your prescriber will determine the right starting dose for you based on your health history and NHS guidance, and will increase your dose gradually over weeks. Understanding the dosing schedule helps you know what to expect when using this medication for healthy weight uk 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.
Mounjaro Dose Schedule and Escalation
Mounjaro is injected once weekly. Each pre-filled KwikPen contains 4 doses (one month's supply). Your prescriber will typically follow this escalation pattern:
- Weeks 1–4: 2.5 mg — starting dose to allow your body to adjust
- Weeks 5–8: 5 mg — first escalation if tolerated well
- Weeks 9–12: 7.5 mg — gradual increase
- Weeks 13–16: 10 mg — continued escalation
- Weeks 17–20: 12.5 mg — penultimate dose
- Week 21 onwards: 15 mg — maximum maintenance dose
You must spend at least 4 weeks on each dose before your prescriber will increase it. This allows your body to adapt and helps minimise side effects. Everyone's escalation timeline is different — your GP or prescriber may adjust this based on how you respond and your individual tolerance.
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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.
Clinical Results and Individual Variation
Clinical trials (SURMOUNT-1) showed that participants using Mounjaro alongside a reduced-calorie diet and increased physical activity lost an average of 15–21% of their body weight — though individual results vary significantly. At the 5 mg dose, average weight loss was approximately 15%, rising to around 20.9% at the maximum 15 mg dose. Weight management outcomes depend on your starting weight, adherence to lifestyle changes, and how your body responds to the medication. Use our GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to track your healthy weight uk progress throughout your treatment journey.
- 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 skip a dose or delay my Mounjaro injection?
If you miss your injection, take it within 4 days of the scheduled date and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next injection on the regular day. Never take a double dose. Maintain at least 72 hours (3 days) between injections. Contact your prescriber if you're unsure.
Will my prescriber automatically increase my dose each month?
No. Your prescriber must assess how you've tolerated the current dose before increasing. If you experience significant side effects or have health concerns, they may delay escalation or keep you on a lower maintenance dose. The dose schedule is flexible based on your individual response and nhs guidance.
What if I can't tolerate a higher dose?
Tell your prescriber immediately. You don't have to reach the maximum 15 mg dose. Many people achieve good weight management results on 5 mg, 10 mg, or 12.5 mg. Your prescriber can keep you on a lower dose that you tolerate well — the goal is sustainable, healthy weight uk management with manageable side effects.
Is 15 mg always the best dose for weight loss?
Not necessarily. Clinical trials showed the highest average weight loss at 15 mg, but individual variation is significant. Some people lose substantial weight at lower doses. Your prescriber will find the optimal dose for you based on effectiveness, tolerability, and your health context. Use our weight converter and bmi calculator to track your progress at each dose level.
How long do I stay on each Mounjaro dose?
Minimum 4 weeks per dose before escalation. Once you reach your optimal maintenance dose (often 10 mg, 12.5 mg, or 15 mg), you'll continue that dose weekly for as long as your prescriber recommends. Treatment duration depends on your goals, health status, and ongoing results. Your prescriber will review this regularly.
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.