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 5 Mg Of Mounjaro?
Each Mounjaro KwikPen contains 0.5ml of liquid per 5mg dose. This means a 5mg dose equals exactly 0.5ml when you inject. Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK. The KwikPen automatically delivers the correct volume for each dose, so you don't need to measure it yourself. Understanding your medication's dosage helps you use it safely and confidently alongside a reduced-calorie diet and increased physical activity.
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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.
Understanding Mounjaro Dosing and Concentration
Mounjaro comes in a pre-filled KwikPen device where the medication is already measured and ready to inject. The concentration of Mounjaro is 2.5mg per 0.2ml, which means a 5mg dose contains exactly 0.5ml of the liquid formulation. Each KwikPen contains four pre-filled doses (a month's supply), and you inject once weekly without needing to manually calculate volumes.
The dose titration process starts at 2.5mg (0.2ml) for weeks 1–4, escalating to 5mg (0.5ml) for weeks 5–8, and potentially increasing further to 7.5mg, 10mg, 12.5mg, or the maximum 15mg dose depending on your response and tolerance. Your prescriber will guide you through this schedule. The KwikPen's design means the needle and injection chamber are pre-calibrated — you simply select your prescribed dose on the pen dial, and it automatically delivers the correct volume.
Unlike insulin pens or some other injectable medications, you cannot adjust the volume yourself. The dose you've been prescribed is the volume your body receives. If you're switching between different doses of tirzepatide or comparing Mounjaro with other GLP-1 medications like Wegovy, your prescriber will manage any changes to ensure continuity of treatment.
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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.
Storage and Safety Information for Mounjaro Injections
Unopened Mounjaro KwikPens must be stored in a refrigerator at 2°C to 8°C and kept in their original carton away from light. Once you start using a pen, it can be kept at room temperature (below 30°C) for up to 30 days. Never freeze Mounjaro — if accidentally frozen, the pen cannot be used and must be discarded safely.
When injecting, rotate your injection sites each week between your stomach (abdomen), upper thigh, or upper arm to prevent skin irritation or lipodystrophy (changes in fat distribution). Always consult your GP or prescriber if you have questions about storage, injection technique, or if you experience unusual side effects. They can also discuss how Mounjaro fits into your overall weight management plan and whether it's appropriate alongside any other medications you're taking.
- 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 5mg Mounjaro the same volume every time I inject?
Yes, exactly. Each 5mg dose in the KwikPen delivers precisely 0.5ml every time. The pen is pre-calibrated, so you simply dial your prescribed dose and inject — the volume is automatic. No a UK pharmacy measuring is required.
Can I use only part of a Mounjaro KwikPen?
No. Each KwikPen is pre-filled with four complete weekly doses. You cannot use a partial dose or save leftover medication. Each pen contains 1ml total (four 0.25ml doses at 2.5mg each). Discard the pen 30 days after first use.
What's the difference between Mounjaro dosing and Wegovy dosing?
Mounjaro (tirzepatide) starts at 2.5mg and escalates to a maximum of 15mg weekly. Wegovy (semaglutide) starts at 0.25mg and reaches a maximum of 2.4mg weekly. Both are once-weekly injections, but Wegovy is a GLP-1 agonist alone, while Mounjaro is a dual GIP/GLP-1 agonist.
How do I know if I'm getting the right Mounjaro dose?
Your prescriber will assess your weight loss, side effects, and health goals to determine the right dose for you. Most people start at 2.5mg and escalate gradually. Your GP or specialist can adjust your dose schedule if needed. Use our GLP-1 weight loss calculator to explore projected outcomes at different doses.
What happens if I miss a Mounjaro injection?
If you miss a dose within 4 days, inject as soon as you remember and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next dose on your normal day. Never take a double dose. Contact your prescriber for guidance if unsure.
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.