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 Dose of Mounjaro?
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK with doses ranging from 2.5 mg to 15 mg. Each dose is injected once weekly as part of a step-by-step titration schedule. Your prescriber will start you on the lowest dose and gradually increase it based on your response and tolerance. Understanding the dosing schedule helps you know what to expect as you progress through treatment alongside lifestyle changes and dietary modifications.
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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 Dosing Schedule and Titration
Mounjaro uses a structured dose titration schedule, meaning you start low and increase gradually every 4 weeks. Each KwikPen contains four weekly injections of the same dose.
- Weeks 1–4: 2.5 mg (starting/adjustment dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
You must stay on each dose for a minimum of 4 weeks before increasing. Your prescriber may keep you on a lower maintenance dose if it's working well and you're tolerating it. Use our GLP-1 weight loss calculator to explore projected weight loss at different doses based on clinical trial data.
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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.
Key Dosing Information and Eligibility
Mounjaro is prescription-only in the UK and requires a clinical assessment to determine eligibility and suitable dose. You're likely eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. Your GP or a licensed prescriber will assess you individually, discuss side effects (nausea, diarrhoea, constipation are common), and establish the right starting point. The GLP-1 mechanism means tirzepatide activates two hormone pathways to support appetite control.
- 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?
The starting dose is 2.5 mg, injected once weekly for 4 weeks. This is the lowest dose to help your body adjust while minimising side effects. After 4 weeks, your prescriber will typically increase to 5 mg if you're tolerating it well.
Can you stay on a lower Mounjaro dose?
Yes. If you're achieving good weight loss results and tolerating a lower dose well (such as 5 mg or 7.5 mg), your prescriber may keep you on that maintenance dose indefinitely rather than continuing to escalate to 15 mg.
What's the difference between Mounjaro and Wegovy doses?
Mounjaro (tirzepatide) and Wegovy (semaglutide) use different dosing schedules. Mounjaro starts at 2.5 mg and maxes at 15 mg weekly, while Wegovy starts at 0.25 mg and maxes at 2.4 mg weekly. They are not directly comparable, and switching requires prescriber guidance.
How long does it take to reach the maximum Mounjaro dose?
Reaching the maximum 15 mg dose takes approximately 20 weeks (5 months) of treatment, assuming you escalate every 4 weeks without delays. Many people stay on lower maintenance doses and never reach 15 mg.
Is Mounjaro available on the NHS in the UK?
NICE has approved tirzepatide (Mounjaro) for NHS use within specialist tier 3/4 weight management services, but availability varies significantly by region and waiting lists can be lengthy. Private prescribing through online services is also available without NHS referral. ```
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.