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 Maximum Dose of Mounjaro?
The maximum dose of Mounjaro in the UK is 15mg, administered once weekly by injection. Mounjaro (tirzepatide) is a prescription-only GIP and GLP-1 receptor agonist licensed for weight management in UK adults. Your prescriber will start you at a lower dose and gradually increase it over several weeks to allow your body to adjust. Most people reach the 15mg maximum dose around week 21 of treatment, though individual progression varies. Not everyone needs to reach the maximum dose—your prescriber will determine the right dose for your needs based on your response and tolerance.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Escalation Schedule
Mounjaro follows a standard dose titration schedule designed to help your body adjust to the medication while minimising side effects. You'll spend a minimum of 4 weeks on each dose before escalating to the next level.
- Weeks 1–4: 2.5mg (starting dose)
- Weeks 5–8: 5mg (first escalation)
- Weeks 9–12: 7.5mg (second escalation)
- Weeks 13–16: 10mg (third escalation)
- Weeks 17–20: 12.5mg (fourth escalation)
- Week 21 onwards: 15mg (maximum maintenance dose)
Your prescriber may keep you at any dose if you're experiencing good results and tolerating it well—reaching 15mg is not mandatory. If you experience troublesome side effects, your dose may be paused or reduced. Each KwikPen contains 4 weekly doses, so a 15mg pen lasts 4 weeks.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Why Start Low and Escalate Gradually?
Starting at 2.5mg and increasing gradually allows your body to adapt to tirzepatide's effects on appetite and digestion. This approach reduces the likelihood of severe nausea, constipation, or diarrhoea—the most common side effects reported in clinical trials. By the time you reach 15mg, your gastrointestinal system has usually adjusted significantly.
Your prescriber's role: They will assess your individual tolerance, monitor your weight loss progress, and check for any concerning side effects at each escalation point. Some people achieve their weight loss goals at 5mg or 10mg and may stay at that dose long-term rather than continuing to 15mg. Use our GLP-1 weight loss calculator to explore how different doses may support your weight loss journey, and our BMI calculator to track your progress alongside the 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.
Is 15mg the dose everyone reaches?
No. Your prescriber determines your individual dose based on your response, tolerance, and weight loss goals. Some people achieve good results at 5mg, 10mg, or 12.5mg and remain on that dose. Reaching 15mg is not a treatment requirement—it's the maximum available, not a target everyone must hit.
What happens if I can't tolerate a higher dose?
If you experience side effects you can't manage, your prescriber may pause escalation or reduce your dose. You can stay on a lower dose long-term. Side effects often improve after 1–2 weeks at each new dose as your body adjusts, so your prescriber may recommend waiting before deciding to reduce.
How long does it take to reach maximum dose?
Following the standard schedule, you'll reach 15mg around week 21 (approximately 5 months) of treatment. However, if your prescriber slows escalation or pauses due to side effects, this may take longer. The timeline is adjusted to your individual needs.
Can I skip doses or escalate faster?
No. The 4-week minimum at each dose is evidence-based to ensure safety and tolerability. Escalating faster increases side effect risk without improving weight loss outcomes. Always follow your prescriber's guidance on dose timing.
What if I miss a dose—does the schedule change?
If you miss a dose by more than 4 days, skip it and continue your normal weekly schedule on your usual day. This doesn't change your overall escalation plan. Always contact your prescriber or pharmacist if you're unsure about missed doses or scheduling changes.
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.