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
What Is 10 ml Mounjaro and How Does It Work?
A 10 ml Mounjaro KwikPen contains four weeks' worth of tirzepatide injections at your prescribed dose. Each pen delivers a once-weekly injection to support weight management. Mounjaro is a dual GIP and GLP-1 receptor agonist—meaning it activates two natural hormone pathways to help reduce appetite and support feeling fuller after meals. It's prescription-only in the UK and requires a clinical assessment before being prescribed. Individual results vary, and Mounjaro works best 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.
How Mounjaro Doses Work and What 10 ml Means
Each Mounjaro KwikPen contains 10 ml of solution, but what matters for your treatment is the dose per injection (in milligrams), not the total volume. The available doses in the UK range from 2.5 mg to 15 mg once weekly. A 10 ml pen typically delivers your prescribed dose for four weeks (four injections). For example, if you're prescribed 5 mg weekly, your 10 ml pen contains four 5 mg doses—one per week for a month.
- Starting dose: 2.5 mg for weeks 1–4
- Maintenance doses: 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg depending on your clinical response
- Escalation: Your prescriber may increase your dose every 4 weeks until an effective maintenance dose is reached
- Storage: Unopened pens stay in the fridge at 2–8°C; after first use, pens can be kept at room temperature (below 30°C) for up to 30 days
The KwikPen is a pre-filled auto-injection device—you don't need to load it or measure doses yourself. Your prescriber will tell you exactly which dose strength to order.
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.
Getting Mounjaro in the UK and What to Expect
In the UK, Mounjaro is available through two routes: NHS specialist weight management services (tier 3) or private online prescribing via a GPhC-registered pharmacy. NHS access typically requires referral from your GP and can involve waiting lists. Private access is faster but costs vary (roughly £160–£250 per month depending on dose). Before prescription, you'll have a clinical assessment to check your eligibility based on BMI and any weight-related health conditions.
Once prescribed, you'll self-inject at home once weekly, rotating injection sites (stomach, thigh, or upper arm). Try our GLP-1 weight loss calculator to project potential outcomes at different doses, and use the BMI calculator to track your starting point and progress alongside Mounjaro use.
- 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 10 ml Mounjaro the same as 10 mg Mounjaro?
No. 10 ml refers to the total volume in the KwikPen (which contains four weekly injections). The dose you inject is measured in milligrams (mg)—typically 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg per injection. Your prescriber will specify which dose strength you need.
How long does a 10 ml Mounjaro pen last?
A 10 ml pen contains four weekly injections, so it lasts approximately four weeks. You'll receive a new pen each month as part of your ongoing prescription, assuming your dose doesn't change.
Can I switch from Mounjaro to Wegovy if I'm not seeing results?
Only your prescriber can advise on switching medications. Mounjaro (tirzepatide) and Wegovy (semaglutide) are different medications with different mechanisms—Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1 only. Any medication change requires clinical reassessment and a new prescription.
What are the main side effects of Mounjaro?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain. These often improve over time as your body adjusts. Less common side effects include indigestion, fatigue, dizziness, and injection site reactions. Seek urgent medical attention for severe stomach pain (possible pancreatitis) or serious allergic reactions.
Is Mounjaro available on the NHS?
Yes, NICE has approved tirzepatide for NHS use within specialist tier 3 weight management services. However, availability varies significantly by region and waiting lists can be long. Your GP can refer you to your local specialist service, or you can access it privately through a licensed prescriber assessment.
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.