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
How Many Ml Is Each Dose Of Mounjaro?
Mounjaro (tirzepatide) comes in specific volumes depending on the dose strength prescribed. Each weekly injection contains a set amount of medication measured in millilitres. In the UK, Mounjaro is available in five different dose strengths, each delivered as a once-weekly injection using a pre-filled KwikPen device. Understanding the exact volume of each dose can help you know what to expect when self-injecting and reassure you that you're receiving the correct amount of medication prescribed by your healthcare provider.
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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 Volumes and Strengths
Each Mounjaro dose is supplied in a specific volume:
- 2.5 mg dose: 0.25 ml
- 5 mg dose: 0.5 ml
- 7.5 mg dose: 0.75 ml
- 10 mg dose: 1.0 ml
- 12.5 mg dose: 1.25 ml
- 15 mg dose: 1.5 ml
These volumes are fixed and cannot be adjusted. The KwikPen device is pre-filled with the exact amount needed for one weekly injection. All doses are administered subcutaneously (under the skin) at the same time each week, typically on the same day. The pen itself contains four weeks' worth of injections, so each pen holds four individual 0.25 ml increments depending on your prescribed dose strength.
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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.
NHS Prescribing and Your Dose
In the UK, Mounjaro is prescribed through NHS specialist weight management services (tier 3) or privately through registered online prescribers following clinical assessment. Your GP or prescriber will determine which dose is appropriate based on your individual health, weight, and response to treatment. Doses are titrated (gradually increased) every four weeks, starting at 2.5 mg, to minimise side effects and find your optimal dose. You must not adjust your dose without guidance from your prescriber. If you miss an injection, contact your prescriber for advice rather than doubling up—the minimum time between injections should be at least 72 hours.
- 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.
Do all Mounjaro pens contain the same volume?
No. Each KwikPen is pre-filled with your specific prescribed dose volume. A 2.5 mg pen contains 0.25 ml per injection, while a 15 mg pen contains 1.5 ml. You receive only the dose your prescriber has chosen for you.
Can I see the volume marked on the Mounjaro pen?
The KwikPen shows the dose strength (2.5 mg, 5 mg, etc.) clearly on the device. The volume in millilitres is not displayed on the pen itself, but your prescribing information and patient leaflet will confirm the exact ml volume for your dose.
What if I accidentally inject more or less than one dose?
Accidental overdose is unlikely with pre-filled pens since each contains exactly one weekly dose. If you're concerned you've used the pen incorrectly, contact your prescriber or NHS 111 immediately for advice rather than taking additional action.
Is the volume the same whether I'm on Mounjaro from the NHS or privately?
Yes. The actual medication and volume are identical regardless of where you're prescribed it. The dose strength you're prescribed determines the volume—2.5 mg is always 0.25 ml, 15 mg is always 1.5 ml, whether NHS or private.
How do I know I'm injecting the full dose volume?
The KwikPen is designed to deliver the full pre-filled dose automatically when you press the injection button. You'll typically feel a click and see the dose counter change. Your prescriber or pharmacist will demonstrate the correct injection technique at the start of treatment.
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.