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 a Mounjaro Dose?
Mounjaro (tirzepatide) is supplied in pre-filled KwikPen devices, not measured in ML by patients. Each pen contains a specific dose in milligrams—ranging from 2.5 mg to 15 mg—delivered as a once-weekly injection under the skin. Unlike some medications measured by volume, Mounjaro doses are standardised by weight, not millilitres. If you're comparing it with Wegovy or wondering about the practical difference between these UK-licensed weight management injections, understanding how they're dosed and delivered can help you make informed conversations with your GP or prescriber.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Measurements vs Wegovy
Mounjaro doses are measured in milligrams (mg), not ML. The tirzepatide in each KwikPen is a fixed dose you don't measure yourself—you simply inject the full contents of the pen. This is different from older GLP-1 medications like Saxenda, which required a UK pharmacy dosing.
- Mounjaro: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg (once weekly)
- Wegovy (semaglutide): 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg (once weekly)
Both medications use pre-filled pens, meaning the dose is pre-measured and you receive the exact amount intended. The key difference isn't volume—it's the mechanism of action. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy works as a GLP-1 agonist only. SURMOUNT clinical trials showed Mounjaro participants lost an average of 15–21% of body weight over 72 weeks, whilst STEP trials showed Wegovy participants lost approximately 15% on average. Individual results vary significantly.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 Is Right for You?
Whether Mounjaro or Wegovy is appropriate depends on your individual health profile, not dose size. Both are prescription-only medicines available through NHS specialist weight management services or private online prescribing following clinical assessment. Your prescriber will consider your BMI, any weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease), and other medications you take.
Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses. Both medications require a reduced-calorie diet and increased physical activity for best results. Neither is a standalone solution. If you're eligible for either medication, your prescriber will explain the dual mechanism advantage of Mounjaro versus the single-action GLP-1 approach of Wegovy, helping you make an informed choice alongside your NHS guidance.
- 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 Mounjaro measured in ML or mg?
Mounjaro is measured in milligrams (mg), not millilitres. Each pre-filled KwikPen contains a fixed dose you inject as-is—you don't measure the volume yourself. Doses range from 2.5 mg to 15 mg, increasing every 4 weeks under clinical guidance.
How much does each Mounjaro injection contain?
Each weekly Mounjaro injection delivers the full dose in your current KwikPen—whether 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg. The pen is pre-filled and single-use. Each KwikPen box contains 4 pens (4 weeks' supply).
Why is Mounjaro different from Wegovy in how it works?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist—activating two hormone pathways. Wegovy (semaglutide) activates GLP-1 only. This dual mechanism may explain why SURMOUNT trials showed slightly higher average weight loss with Mounjaro (~20%) versus Wegovy (~15%), though results vary individually.
Do I need to know the ML volume to use Mounjaro?
No. You receive a pre-filled KwikPen with no dose calculation required. Your prescriber manages the dose titration schedule. You simply inject once weekly on the same day. Always follow your prescriber's instructions on when to increase doses.
Can I switch between Mounjaro and Wegovy doses?
Approximate dose equivalences exist (5 mg Mounjaro ≈ 0.5 mg Wegovy; 15 mg ≈ 2.4 mg), but any switch must be managed by your prescriber. Never self-adjust or swap medications without clinical guidance. Your GP or weight management service will advise on transitions if needed.
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.