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 Dosages — Complete UK Dosing Guide
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK with a clear dosing schedule. The medication is given as a once-weekly injection starting at 2.5 mg, with doses gradually increased over 20 weeks to a maximum of 15 mg. Understanding the dosing schedule, how titration works, and what each dose means is essential for anyone considering this treatment. This guide explains the complete Mounjaro dosing pathway, how your prescriber manages dose increases, and what to expect at each stage of treatment.
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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.
How Mounjaro Dosing Works — The Titration Schedule
Mounjaro is supplied as a once-weekly injectable pen called a KwikPen, with each pen containing 4 doses—one month's supply. The dosing schedule is carefully designed to allow your body to adjust to the medication gradually. Your prescriber will not increase your dose until you have been on each dose for a minimum of 4 weeks.
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg (second escalation)
- Weeks 13–16: 10 mg (third escalation)
- Weeks 17–20: 12.5 mg (fourth escalation)
- Week 21 onwards: 15 mg (maximum dose)
This titration approach helps minimise side effects and allows your prescriber to find the most effective dose for your individual needs. Some people benefit from staying at lower doses like 5 mg or 10 mg, whilst others continue to the maximum 15 mg dose. Your tirzepatide prescription is personalised—there is no one-size-fits-all 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.
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When Does Your Dose Get Adjusted, and What If You Miss a Dose?
Dose escalation happens every 4 weeks if you and your prescriber agree to increase. If you experience significant side effects at any dose, your prescriber may decide to keep you at that dose for longer or not increase further. Never increase your dose without guidance from your prescriber.
If you miss a dose: within 4 days of the scheduled injection, take it as soon as you remember and continue on your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next one on the normal day. You need at least 72 hours (3 days) between injections. Use our free GLP-1 weight loss calculator to explore how different doses may affect your weight loss journey, and track your progress with our progress tracker once you begin treatment.
- 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 you skip the Mounjaro titration schedule and start at a higher dose?
No. The 4-week minimum at each dose is standard practice to allow your body to adjust and minimise side effects. Starting too high risks severe nausea and digestive symptoms. Your prescriber will follow the titration schedule unless there is a specific medical reason not to.
What if Mounjaro side effects are too strong at your current dose—can you stay at a lower dose permanently?
Yes, absolutely. Many people find their optimal dose at 5 mg, 10 mg, or 12.5 mg rather than the maximum 15 mg. Your prescriber may recommend staying at a lower dose if you are seeing good results and tolerating it well. Effectiveness varies—higher doses are not necessary for everyone.
Is there a difference between the Mounjaro KwikPen doses—do different coloured pens mean different strengths?
The KwikPen colours indicate the dose strength (each colour represents a different dose), and each pen contains 4 injections. Your pharmacy will dispense the correct coloured pen for your prescribed dose. Each injection from that pen delivers the same dose—you do not choose individual injection amounts.
How does Mounjaro dosing compare to Wegovy dosing?
Mounjaro (tirzepatide) and Wegovy (semaglutide) use different dosing schedules. Mounjaro starts at 2.5 mg and goes up to 15 mg weekly, whilst Wegovy starts at 0.25 mg and reaches 2.4 mg. Approximate equivalence suggests Mounjaro 5 mg ≈ Wegovy 0.5 mg, but these are different medications requiring different prescriber guidance.
What happens to your dosing if you want to stop Mounjaro treatment?
You simply stop taking injections—there is no tapering requirement. However, discuss stopping with your prescriber, as weight regain can occur. Some people continue at a maintenance dose long-term, whilst others cycle off and restart later. Your GP or prescriber will guide the best approach for your individual situation.
Ready to take control of your weight loss journey?
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