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
Mounjaro Dose in ml — How Much Does Each Pen Contain?
Mounjaro (tirzepatide) is supplied as pre-filled KwikPen injection devices, but doses are measured in milligrams (mg), not millilitres (ml). Each KwikPen contains 4 weeks' worth of injections at a single dose strength. Understanding your prescription dose is important for managing your weight loss treatment safely and knowing what to expect from your GP or private prescriber.
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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 Strengths and KwikPen Supply
Mounjaro is available in six dose strengths, each supplied in a pre-filled KwikPen device. Important clarification: Mounjaro doses are measured in milligrams (mg), not millilitres (ml). Each KwikPen contains 4 weeks of treatment at a single dose. The available dose strengths are:
- 2.5 mg — starting dose (weeks 1–4)
- 5 mg — first maintenance dose (weeks 5–8)
- 7.5 mg — escalation dose (weeks 9–12)
- 10 mg — escalation dose (weeks 13–16)
- 12.5 mg — escalation dose (weeks 17–20)
- 15 mg — maximum maintenance dose (week 21 onwards)
Each KwikPen is a single-dose-strength device — you cannot adjust the dose yourself. Your prescriber will write a prescription for the specific dose strength needed at each stage of your treatment plan. You cannot mix doses or split pens between different dose levels.
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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.
Dose Titration and What to Expect
Your Mounjaro treatment follows a gradual titration schedule, meaning your dose increases over time. You stay on each dose for a minimum of 4 weeks before escalating to the next strength. This allows your body to adjust and helps minimise side effects. Not everyone escalates to the maximum 15 mg dose — your prescriber will assess your response and may maintain you at a lower dose if it is effective. Our free GLP-1 weight loss calculator can help you understand potential weight loss ranges at different dose levels based on clinical trial data.
- 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 does "dose in ml" mean for Mounjaro?
Mounjaro doses are expressed in milligrams (mg), not millilitres (ml). This is a common source of confusion. The medication is supplied in a pre-filled KwikPen pen, but the clinical dose is always referred to and prescribed in mg — such as 2.5 mg, 5 mg, or 15 mg. Each pen delivers a single fixed dose.
How much Mounjaro is in each KwikPen?
Each KwikPen contains 4 weeks' worth of Mounjaro at a single dose strength. For example, a 10 mg KwikPen contains four separate 10 mg injections — one per week for 4 weeks. You cannot use a pen for longer than 30 days after first use, even if injections remain.
Can I adjust my Mounjaro dose myself?
No. Each KwikPen is pre-filled with a fixed dose that you cannot adjust. Dose changes require a new prescription from your GP or licensed prescriber. You must use the exact dose prescribed and follow the weekly injection schedule. Never attempt to alter doses.
What is the starting dose of Mounjaro in the UK?
The standard UK starting dose is 2.5 mg once weekly. You remain on this dose for 4 weeks, then progress to 5 mg for the next 4 weeks. Escalation continues at 4-week intervals unless your prescriber advises otherwise or you experience side effects requiring a slower titration.
How do Mounjaro doses compare to Wegovy doses?
Mounjaro and Wegovy (semaglutide) use different dosing schedules. Mounjaro starts at 2.5 mg and reaches a maximum of 15 mg. Wegovy starts at 0.25 mg and reaches a maximum of 2.4 mg. They are not directly equivalent — your prescriber will choose the most appropriate medication and dosing for your individual needs following clinical assessment.
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.