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
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Mounjaro Counting Clicks vs Wegovy — What's the Difference?
If you've been prescribed or are considering a GLP-1 weight loss injection in the UK, you may have heard about "counting clicks" on the Mounjaro KwikPen device. This refers to how doses are delivered via the pen's click mechanism. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) work differently in how they're administered, and understanding these differences can help you make an informed decision with your prescriber. This guide compares the two medications factually to help you understand what to expect.
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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 and Wegovy Injections Differ
Mounjaro (tirzepatide) uses a pre-filled KwikPen device where each click delivers 0.1 mg of medication. To reach your prescribed dose, you count the clicks—for example, a 2.5 mg dose requires 25 clicks. Each KwikPen contains four pre-loaded doses (four weeks' supply) and is injected once weekly.
Wegovy (semaglutide) also uses a pre-filled auto-injection pen, but the mechanism differs slightly. Wegovy pens come in fixed-dose strengths (0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg), meaning you select the appropriate pen strength rather than counting clicks to reach your dose. Wegovy is also injected once weekly.
The key difference is mechanical: Mounjaro requires a UK pharmacy click counting; Wegovy uses fixed-dose pens. Both are equally effective when used correctly, and the choice between them depends on clinical assessment and individual suitability, not on device preference.
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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.
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SURMOUNT vs STEP Trial Results — Clinical Context
In clinical trials, both medications demonstrated significant weight loss. Mounjaro (SURMOUNT-1 trial) showed average weight loss of approximately 15–21% of body weight at maximum dose over 72 weeks. Wegovy (STEP-1 trial) showed average weight loss of approximately 14.9% at maximum dose over 68 weeks.
Important: Individual results vary significantly. These are trial averages, not assured outcomes. Both medications work by activating GLP-1 pathways but through different mechanisms—Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is a GLP-1-only agonist. Your GP or prescriber will assess which medication is suitable for you based on your health profile, not on device mechanism.
Both Mounjaro and Wegovy are prescription-only medicines in the UK requiring clinical assessment before dispensing. You cannot choose between them based on personal preference alone—your prescriber makes this decision based on your individual health status, medical history, contraindications, and previous medication responses. If one medication is unsuitable, your prescriber may suggest the alternative. Use our GLP-1 weight loss calculator to estimate potential weight loss outcomes with either medication, and discuss with your healthcare provider which option is right for you.
- 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.
What does "counting clicks" on Mounjaro mean?
Mounjaro's KwikPen requires you to count clicks to deliver your prescribed dose. Each click equals 0.1 mg. For example, a 5 mg dose requires 50 clicks. The pen has an audible click and a dose counter window so you can confirm you've reached the correct number of clicks before injecting.
Does Wegovy use the same clicking mechanism?
No. Wegovy uses fixed-dose auto-injection pens—you simply select the pen strength your prescriber has prescribed (0.25 mg, 0.5 mg, 1 mg, 1.7 mg, or 2.4 mg) and inject without counting. This may be easier for some users, but both devices are equally safe and effective.
Which medication is better—Mounjaro or Wegovy?
Neither is objectively "better." Both are UK-licensed for weight management. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist; Wegovy (semaglutide) is a GLP-1-only agonist. Clinical trials show similar weight loss results. Your prescriber will recommend based on your individual health profile, not device preference.
Can I switch from Mounjaro to Wegovy if I don't like counting clicks?
Device preference alone is not a clinical reason to switch medications. However, if you experience side effects or the medication isn't working well for you, discuss alternatives with your GP. Any medication switch requires clinical assessment and your prescriber's approval.
How do I know if Mounjaro or Wegovy is available to me on the NHS in the UK?
Both medications are NICE-approved for NHS use through specialist tier 3 weight management services. However, NHS availability varies significantly by region and waiting lists can be very long. Your GP can refer you to your local specialist weight management service. Private prescribing is also available through registered online pharmacies following a clinical assessment.
Ready to take control of your weight loss journey?
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