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 Does a Mounjaro Pen Have?
A Mounjaro KwikPen doesn't use "clicks" in the traditional sense — instead, you hold down the button for 3 seconds to deliver the full weekly dose. Unlike older pen devices, the Mounjaro KwikPen is a simpler auto-injector that delivers the entire dose automatically once activated. This differs from Wegovy pens, which also use automatic injection but have different handling. Understanding how your pen works is essential before your first injection. If you're considering either tirzepatide or semaglutide for weight management, knowing the injection mechanics helps you feel confident about treatment.
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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 vs Wegovy: Injection Mechanism Comparison
Mounjaro KwikPen is a pre-filled auto-injector device that delivers the full dose in a single injection. You do not dial doses or count clicks — simply hold the button down for 3 seconds, and the pen automatically administers the entire weekly dose of tirzepatide. The needle retracts automatically after injection. Each KwikPen contains 4 pre-filled doses (4 weeks' supply), and you dispose of the pen after the fourth injection.
Wegovy auto-injection pens similarly use automatic injection technology. You press and hold the button for 3 seconds to deliver the semaglutide dose. Like Mounjaro, each pen contains multiple pre-filled doses and the needle retracts automatically. Both devices are designed for ease of use — no a UK pharmacy dose adjustment required.
Key difference: The underlying mechanism differs — Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist, whilst Wegovy contains semaglutide, a GLP-1 agonist only. Clinical trials (SURMOUNT for Mounjaro, STEP for Wegovy) showed different weight loss outcomes, though 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.
Choosing Between Mounjaro and Wegovy: What Matters More
Neither "clicks" nor injection ease should determine your choice between Mounjaro and Wegovy — both are prescription-only medicines requiring clinical assessment and a prescription from a UK-licensed prescriber. Your eligibility, medical history, and individual response are what matter. Try our GLP-1 weight loss calculator to explore projected outcomes at different doses, and use our BMI calculator to check your starting point. Your GP or prescriber will assess whether tirzepatide or semaglutide is more suitable for you based on your health profile. Access in the UK is through NHS specialist weight management services or private online prescribing following a clinical consultation.
- 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 Mounjaro pen have clicks like older insulin pens?
No. The Mounjaro KwikPen is a modern auto-injector — you simply press and hold the button for 3 seconds to deliver the full dose automatically. There are no clicks or a UK pharmacy dose adjustments. This makes it simpler to use than older dial-up pen designs.
How many doses are in one Mounjaro KwikPen?
Each Mounjaro KwikPen contains 4 pre-filled doses, representing a 4-week supply (since Mounjaro is injected once weekly). After the fourth injection, you dispose of the pen and start a new one.
Is the Wegovy injection mechanism the same as Mounjaro?
Both use automatic injection pens where you hold the button for 3 seconds. The main difference is the active ingredient — Mounjaro contains tirzepatide (dual GIP+GLP-1) and Wegovy contains semaglutide (GLP-1 only). Clinical trial data shows different average weight loss outcomes, though results vary between individuals.
Can I reuse a Mounjaro KwikPen?
No. Each Mounjaro KwikPen is single-use for 4 weeks only. After your fourth injection, dispose of it safely (in a sharps bin or as directed by your pharmacist) and use a new pen. Never attempt to refill or reuse a pen.
What if I find the Mounjaro pen difficult to use?
Speak to your pharmacist or prescriber. They can provide injection training, observe your technique, and discuss any concerns. Some people prefer Saxenda (liraglutide), which is a daily injection with a different device. Your prescriber can help you find the option that works best for you.
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.