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 For 5mg From A 7.5mg Pen?
If you're using a Mounjaro KwikPen and need to dial a lower dose, this is an important question about safe medication administration. The short answer: a 7.5mg KwikPen cannot be dialled down to deliver exactly 5mg. Each KwikPen is pre-filled with a specific dose, and the dial mechanism is designed to deliver that full dose only. If you need a 5mg dose, you require a separate 5mg KwikPen pen. This UK health guide explains how the pen works and why dose adjustment isn't possible with the current device design.
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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 KwikPen Dosing Works
Mounjaro comes in pre-filled KwikPens, each containing a single fixed dose. The available doses are 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, and 15mg per injection. Each pen is manufactured to deliver its specific dose and cannot be adjusted downwards to a lower amount.
The KwikPen dial mechanism works by rotating a numbered dial to select your dose, but these numbers correspond to pre-set doses only, not to variable amounts. If your prescriber adjusts your dose from 7.5mg down to 5mg (or any other reduction), you will need a new 5mg KwikPen—you cannot use the 7.5mg pen to achieve this. This design ensures dose accuracy and prevents medication errors.
Always check your pen's label before each injection to confirm you have the correct dose prescribed by your GP or specialist. If you have been prescribed a different dose, contact your prescriber or pharmacy for a replacement pen before your next scheduled injection.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
What To Do If Your Dose Changes
If your prescriber reduces your Mounjaro dose from 7.5mg to 5mg (or adjusts it to any other strength), do not attempt to use your existing 7.5mg pen. Instead, request a replacement from your pharmacy—specifically a 5mg KwikPen.
Dose adjustments are common during Mounjaro treatment as your prescriber optimises the medication for your health needs. Keep at least one week's supply of your current dose available so you don't miss an injection while waiting for a replacement pen. Store new pens in the refrigerator at 2–8°C in their original carton until needed. If you're unsure about your prescribed dose or whether your pen is correct, always check with your GP or pharmacist before injecting.
- 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.
Can I dial down a 7.5mg KwikPen to 5mg?
No. The KwikPen dial system cannot be adjusted to deliver a lower dose than the pen contains. Each pen delivers its pre-set, fixed dose only. If your dose changes to 5mg, you need a separate 5mg KwikPen from your pharmacy.
What should I do if I've been prescribed a lower dose?
Contact your pharmacy or prescriber and request the correct strength KwikPen for your new dose. Do not attempt to modify or reuse a higher-dose pen. Your pharmacy will issue a replacement pen at no additional cost if it's an NHS prescription.
Why can't Mounjaro pens be adjusted to lower doses?
The KwikPen design ensures accurate, safe medication delivery. Pre-set doses prevent calculation errors and ensure consistent treatment. Attempting to modify the mechanism risks incorrect dosing and potential harm.
What if I accidentally use the wrong dose pen?
Contact your GP, prescriber, or NHS 111 immediately. Do not use the pen again. They can advise whether additional medical assessment is needed and ensure you receive the correct pen for your prescribed dose.
How often can my Mounjaro dose be adjusted?
Your prescriber typically increases your dose gradually (every 4 weeks minimum) based on your response and tolerance. Decreases are less common but may happen if you experience side effects. Always discuss dose changes with your GP or specialist before changing your routine.
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.