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 Pen Clicks Chart and Wegovy Comparison
Understanding your Mounjaro KwikPen clicks and how tirzepatide compares to Wegovy can help you make informed decisions about weight management treatment. Both are prescription-only weight loss injections available in the UK, but they work differently and use different dosing systems. This guide explains the key differences, eligibility criteria, and what to expect from each medication. Remember, your GP or prescriber will assess which option is most suitable for you based on your individual health needs.
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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 vs Wegovy — Mechanism and Dosing
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. The Mounjaro KwikPen delivers doses from 2.5 mg up to 15 mg once weekly. Each pen contains four doses (four weeks' supply). Dose titration typically starts at 2.5 mg and increases every four weeks if needed.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates a single hormone pathway. Wegovy doses range from 0.25 mg to 2.4 mg, also given once weekly. The titration schedule is more gradual, progressing through five dose levels over approximately 16 weeks.
In UK clinical trials, Mounjaro showed average weight loss of 15–21% of body weight, whilst Wegovy showed approximately 15% in STEP trial data. Both results were achieved alongside reduced-calorie diet and increased physical activity, and individual results vary significantly. Your prescriber will discuss which mechanism and dosing schedule suits your UK prescription needs.
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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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Eligibility, Side Effects, and Finding the Right Option
Both medications are available on the NHS through specialist weight management services (tier 3), though waiting lists vary by region and ICB. Private access is also available following an online clinical assessment with a UK-licensed prescriber.
Eligibility is the same for both: BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Side effects are similar and typically include nausea, diarrhoea, constipation, and abdominal discomfort — most improve with dose titration. Your GP or prescriber will assess whether Mounjaro, Wegovy, or another approach is most appropriate for you. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to understand your current health risk category.
- 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 is the difference between Mounjaro's GIP+GLP-1 mechanism and Wegovy's GLP-1-only mechanism?
Mounjaro activates two hormone pathways (GIP and GLP-1), whilst Wegovy activates GLP-1 only. The dual mechanism may help some people achieve slightly greater weight loss on average, but both medications work by reducing appetite and supporting fullness. Individual response varies — one medication may suit you better than the other based on your health profile and side effect tolerance.
How do I know if the Mounjaro KwikPen clicks match my prescribed dose?
Your prescriber or pharmacist will explain exactly how many pen clicks correspond to your dose. The Mounjaro KwikPen is designed to deliver the correct dose automatically — you do not need to count clicks yourself. Always check the pen label and pharmacist's instructions for your specific dose (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg).
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official established conversion chart between tirzepatide and semaglutide doses — any switch requires a new clinical assessment. Your GP or prescriber will decide if switching is appropriate and how to do it safely based on your response to the current medication.
Are Mounjaro and Wegovy available on the NHS in the UK?
Yes, both are approved for NHS use in specialist weight management services (tier 3). NHS access varies by region and involves referral from your GP. Both are also available privately following an online assessment with a UK-licensed prescriber. Your GP can advise on NHS options in your area and waiting times.
Which medication causes fewer side effects — Mounjaro or Wegovy?
Both medications have similar side effect profiles, with nausea, diarrhoea, and constipation being most common. Side effects typically improve as your body adjusts during dose titration. Individual tolerance varies widely — some people experience fewer side effects on one medication than the other. Your prescriber will monitor you and can adjust your dose or consider alternatives if side effects are problematic.
Ready to take control of your weight loss journey?
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