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 Clicks on a Mounjaro Pen?
A Mounjaro KwikPen doesn't work with "clicks" — instead, each pre-filled pen contains a single dose that you inject once weekly. The pen automatically delivers your prescribed dose (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg) when you press the injection button. Each KwikPen is used once, then disposed of safely. Understanding how to use your Mounjaro pen correctly is essential for effective treatment, whether you're accessing it through NHS tier 3 specialist services or via private prescribing in the UK.
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.
How Mounjaro KwikPen Dosing Works
Mounjaro comes as a pre-filled KwikPen injection device, not a multi-dose vial or click-counter pen. Each KwikPen contains one complete dose of tirzepatide, ready to inject. The pen is designed for single use only — you inject your weekly dose by pressing the injection button until you hear a click, then hold for 3 seconds. The click signals the injection is complete. Each box contains 4 pens (one month's supply), so you'll use one new pen each week.
Dose titration schedule: Your prescriber will start you on 2.5 mg and increase the dose every 4 weeks (2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg maximum). Each dose increase means receiving a new strength of KwikPen — you don't adjust clicks or settings on the same pen. This step-wise approach allows your body to adapt and helps manage side effects like nausea.
Using our GLP-1 weight loss calculator above can help you understand projected outcomes at different dose levels during your titration journey.
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.
NHS Prescribing and Mounjaro Availability in the UK
Mounjaro (tirzepatide) is NICE-approved for NHS use within specialist weight management services (tier 3). Access is through referral from your GP to your local integrated care board's specialist service, not standard GP prescription. Waiting times for NHS tier 3 services vary significantly by region — some areas have waits of 12+ months.
Private prescribing option: You can also obtain a Mounjaro prescription through UK-licensed online prescribers following a clinical assessment, then collect from a GPhC-registered pharmacy. This route typically has faster access but involves private costs. Regardless of NHS or private route, you'll receive clear instructions on KwikPen injection technique from your prescriber or pharmacist before starting 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.
How do I know when my Mounjaro injection is finished?
You'll hear and feel a click when the injection button reaches the end of its travel. This signals the full dose has been delivered. Hold the pen against your skin for 3 seconds after the click to ensure all medication is injected. If you're unsure, your pharmacist or GP can demonstrate the technique.
Can I reuse a Mounjaro KwikPen?
No. Each KwikPen is single-use only and should be disposed of safely in a sharps bin after one injection. Never attempt to reuse a pen — it cannot be refilled and the injection mechanism only works once.
What if I don't hear a click when injecting my Mounjaro pen?
Contact your pharmacist or GP immediately. You may not have received the full dose. Never use the same pen again. Get a replacement pen and follow injection instructions carefully. Your healthcare provider can observe your technique if needed.
How do I dispose of my used Mounjaro pens safely?
Place used KwikPens in a sharps bin — never in regular household waste. Your pharmacy will provide a sharps bin if you collect Mounjaro privately. On NHS, your GP practice can arrange safe disposal. Never throw pens in the recycling or general rubbish.
Does the Mounjaro dose increase mean I get a different pen?
Yes. Each dose level (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg) comes as a separate KwikPen strength. During dose titration, your prescriber will provide new pens at each strength increase — you don't adjust anything on the pen itself.
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.