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?
Each Mounjaro KwikPen contains a fixed volume of tirzepatide solution, with the actual dose amount (in milligrams) varying by your treatment stage. The ml volume remains consistent across all dose strengths — the medication concentration changes instead. Understanding the volume and dose progression is important when accessing Mounjaro in the UK, whether through NHS specialist services or private prescription routes.
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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 KwikPen ml Volume and Dose Progression
Each Mounjaro KwikPen pre-filled injection pen contains approximately 1.5 ml of solution. This volume is the same for all dose strengths — what changes is the concentration of tirzepatide within that 1.5 ml. The dose you receive depends on your treatment stage, which typically follows a titration schedule over several weeks.
- Weeks 1–4: 2.5 mg starting dose
- Weeks 5–8: 5 mg escalation dose
- Weeks 9–12: 7.5 mg escalation dose
- Weeks 13–16: 10 mg escalation dose
- Weeks 17–20: 12.5 mg escalation dose
- Week 21 onwards: 15 mg maximum maintenance dose
Each KwikPen is single-use and provides four weekly injections (one month's supply). You'll rotate injection sites weekly between your stomach, thigh, and upper arm to minimise irritation.
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.
Accessing Mounjaro in the UK: NHS vs Private Routes
In the UK, Mounjaro access depends on your chosen route. NHS access is available through specialist tier 3 weight management services following a GP referral, but waiting times vary significantly by region and service availability. Private access is available through GPhC-registered online prescribing services — you complete an online clinical assessment with a UK-licensed prescriber, receive a prescription if appropriate, and it's dispensed by a registered pharmacy.
Private Mounjaro costs typically range from £129–£320 per month depending on dose strength and provider. Your prescriber will assess your eligibility based on BMI (30+, or 27–29.9 with weight-related health conditions) and medical history. Try our free GLP-1 weight loss calculator to estimate potential results with tirzepatide treatment.
The online prescription process usually takes 24–48 hours from assessment to dispensing. You'll need to provide details of your medical history, current medications, and any allergies. Once prescribed, your KwikPens are sent to your home address. Storage is straightforward — unopened pens stay in the fridge at 2–8°C, and after first use can be kept at room temperature (below 30°C) for up to 30 days. Always inform your GP that you're taking Mounjaro, especially if you take other medications like oral contraceptives or diabetes treatments that may interact.
- 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.
Does the ml volume change between different Mounjaro doses?
No. All Mounjaro KwikPens contain 1.5 ml of solution regardless of dose strength. The mg amount changes (2.5 mg to 15 mg), but the injection volume stays the same. This is because the concentration of tirzepatide within that 1.5 ml varies by dose.
How long does one Mounjaro KwikPen last?
One KwikPen contains four weekly doses (one month's supply). After your first injection, you use the same pen for three more weeks before moving to the next KwikPen. Each pen is single-use and should be disposed of after the fourth injection.
What's the difference between Mounjaro and Wegovy injections?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates GLP-1 only. Mounjaro uses KwikPens with 1.5 ml volume per dose. Wegovy uses pre-filled pens with smaller volumes. Both are once-weekly injections, but dosing schedules and maximum doses differ.
Can I access Mounjaro on the NHS in the UK?
Yes, but availability is limited. Mounjaro is approved by NICE for NHS use through specialist tier 3 weight management services. Access requires a GP referral and depends on your regional ICB's commissioning. Many areas have long waiting lists. Private prescription is often faster and doesn't require an NHS referral.
What happens if I miss a Mounjaro injection?
If you miss a dose within 4 days of when you should have taken it, inject as soon as you remember and continue your normal schedule. If more than 4 days have passed, skip that dose and take your next injection on your normal scheduled day. Never double-dose, and maintain at least 72 hours between injections.
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.