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 Millilitres Is 2.5 Mg Of Mounjaro?
The 2.5 mg starter dose of Mounjaro contains 0.625 ml of tirzepatide solution in each pre-filled KwikPen. This is the standard opening dose when starting treatment, designed for your body to adjust to the medication over the first four weeks. Understanding your Mounjaro dose in both milligrams and millilitres can help you track your prescription accurately. If you're comparing Mounjaro with other weight loss injections like Wegovy (semaglutide), it's helpful to understand how these medications differ in strength, delivery, and how they're used in UK weight management. Use our GLP-1 weight loss calculator to explore how different doses might support your weight management journey.
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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 vs Wegovy: Dose Strength And Mechanism Differences
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only GLP-1 based weight loss injections licensed in the UK, but they work differently and come in different dose strengths.
- Mounjaro: A dual GIP + GLP-1 receptor agonist. The 2.5 mg dose (0.625 ml) is the starting dose, with escalation through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum over several weeks.
- Wegovy: A GLP-1 receptor agonist only. Starting dose is 0.25 mg (0.75 ml), escalating to 0.5 mg, 1 mg, 1.7 mg, and up to 2.4 mg maximum.
- Key difference: Mounjaro's dual mechanism activates two hormone pathways (GIP and GLP-1), whilst Wegovy activates GLP-1 only. Clinical trials showed Mounjaro users lost an average of 20.9% of body weight at maximum dose, compared to approximately 15% for Wegovy.
- Prescription and assessment: Both require a clinical assessment from a UK-licensed prescriber. Availability through NHS specialist services varies by region; private online prescribing is also available through registered pharmacies.
Individual suitability depends on your medical history, other medications, and your prescriber's assessment—no two patients are identical in how they respond.
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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.
Which Medication Is Right For You? Individual Factors Matter Most
Choosing between Mounjaro and Wegovy is not about which is "better"—both are effective, licensed medications for weight management in UK adults. Your prescriber will assess which is more suitable based on your health profile, any existing conditions, and drug interactions. Factors your prescriber may consider include whether you have type 2 diabetes, how your body responds to different mechanisms, any previous medication reactions, and your personal preferences.
Both medications are typically prescribed alongside a reduced-calorie diet and increased physical activity. Results vary significantly between individuals—some people respond better to Mounjaro's dual mechanism, whilst others find Wegovy equally effective. Use our BMI calculator to track where you sit on the NHS health scale, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses. Always discuss any concerns with your GP or prescriber before starting or changing weight loss treatment.
- 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 2.5 mg Mounjaro the same strength as any Wegovy dose?
No. The 2.5 mg Mounjaro starter dose (0.625 ml) is not directly equivalent to any Wegovy dose. Wegovy starts at 0.25 mg. Approximate equivalences suggest 2.5 mg Mounjaro ≈ 0.25–0.5 mg Wegovy, but these are not official conversions. Any switch between medications must be managed by your prescriber.
How is Mounjaro dose measured—by mg or ml?
Mounjaro is prescribed and dosed in milligrams (mg), not millilitres. However, each pre-filled KwikPen contains a specific volume in ml. The 2.5 mg dose contains 0.625 ml. Your prescriber will refer to doses in mg, and the pharmacy dispenses the pre-filled pen accordingly.
Can I switch from Mounjaro 2.5 mg to Wegovy if the first dose isn't right for me?
Possibly, but only under your prescriber's guidance. Switching between different weight loss medications requires a clinical decision. Your prescriber will assess whether a switch is appropriate, any washout period needed, and how to transition safely. Never stop or change medication without consulting your prescriber.
What happens after four weeks on 2.5 mg Mounjaro?
After four weeks on the 2.5 mg starter dose, your prescriber will typically increase you to 5 mg if tolerated well. Doses are escalated gradually every four weeks, up to a maximum of 15 mg, based on your response and side effects. Your prescriber guides this escalation schedule.
Is Mounjaro available through the NHS in the UK?
Yes, Mounjaro (tirzepatide) is approved by NICE for NHS use within specialist tier 3 weight management services. However, NHS access is limited and varies significantly by region. Private online prescribing through registered pharmacies is an alternative route if you meet clinical eligibility criteria.
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.