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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How Many Ml Is 2.5 Mg Of Mounjaro?
The 2.5 mg starting dose of Mounjaro (tirzepatide) is delivered as 0.36 ml of solution in a pre-filled KwikPen injection device. Each KwikPen contains four weekly doses and comes with clear markings to help you inject the correct amount. Understanding the volume helps you recognise what to expect when you first use your pen, though you won't need to measure it manually—the KwikPen is pre-filled and calibrated to deliver the exact dose automatically.
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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.
Understanding Mounjaro Doses And The KwikPen Device
Mounjaro is supplied as a pre-filled KwikPen injection device, meaning the dose volume is already calculated and measured for you. You don't manually draw up the injection—you simply dial the dose selector on the pen to the number corresponding to your prescribed dose (2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, or 15mg), and the pen delivers the correct volume automatically. The 2.5mg dose is the starting dose for most patients beginning Mounjaro treatment in the UK. Each KwikPen contains four weekly injections, making it a one-month supply. The pen stores safely in a refrigerator at 2–8°C before first use. After your first injection, you can keep the same pen at room temperature (below 30°C) for up to 30 days. When comparing Mounjaro vs Wegovy, both are once-weekly injections, but they work differently—Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates GLP-1 alone. Your prescriber will determine which medication suits your individual circumstances.
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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.
Mounjaro Dose Titration Schedule And NHS Access
Mounjaro dose titration means gradually increasing your dose every four weeks. You begin at 2.5mg and step up to 5mg, then 7.5mg, 10mg, 12.5mg, and finally 15mg, depending on your response and how well you tolerate each dose. In the UK, Mounjaro is available through NHS specialist weight management services (tier 3/4) for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or hypertension. However, NHS access varies by region and waiting lists can be lengthy. Many people access Mounjaro privately through UK-licensed prescribers following an online clinical assessment. Our GLP-1 weight loss calculator can help you explore potential weight loss at different doses based on clinical trial data, though individual results vary significantly.
- 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 0.36ml of Mounjaro the same as 2.5mg?
Yes. The 2.5mg starting dose is delivered as 0.36ml in the KwikPen. Mounjaro is measured by active ingredient dose (milligrams), not by volume. You select the dose on the pen dial—you don't measure volume yourself. The pen automatically delivers the correct amount.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is available through NHS specialist weight management services for eligible adults. NICE has approved it for use within NHS tier 3/4 services. However, availability varies by region, and waiting lists can be very long. Private access through a UK-licensed prescriber is also available without NHS referral.
How does Mounjaro differ from Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only agonist. Both are once-weekly injections. In clinical trials, Mounjaro showed average weight loss of 15–21%, while Wegovy showed approximately 15%. Your prescriber will assess which is suitable for you based on your health profile.
What are the main side effects of Mounjaro at the starting dose?
The most common side effects include nausea, diarrhoea, vomiting, and stomach pain—especially when starting. These often improve as your body adjusts. More serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems. Always report concerning symptoms to your prescriber.
Do I need a prescription to buy Mounjaro in the UK?
Yes. Mounjaro is prescription-only and requires a clinical assessment by a UK-licensed prescriber before you can obtain it. Private prescribers conduct online assessments to determine eligibility based on your BMI, health conditions, and medical history. You cannot buy it over the counter.
Ready to take control of your weight loss journey?
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