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
Can Mounjaro Be Kept Out Of The Fridge After Use?
Yes, Mounjaro can be kept out of the fridge, but only after you've started using it. Once you inject your first dose from a KwikPen, you can store it at room temperature (below 30°C) for up to 30 days. Before first use, your tirzepatide pens must stay refrigerated at 2–8°C. Understanding the correct storage requirements helps ensure your prescription medication stays safe and effective throughout your weight management treatment.
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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.
Mounjaro Storage Rules — Before And After First Use
Before first injection: Store unopened Mounjaro KwikPens in a refrigerator at 2°C to 8°C. Keep them in the original carton to protect from light. Do not freeze—if a pen has been frozen, do not use it. Unopened pens can be stored this way until the expiry date printed on the carton.
After first injection: Once you've used your first dose from a KwikPen, you can remove it from the fridge and store it at room temperature below 30°C for up to 30 days. Mark the date you first used the pen so you know when the 30-day window closes. After 30 days, safely dispose of the pen even if there are doses remaining.
Important: Never store Mounjaro in direct sunlight, near heat sources, or in a hot car. If your home temperature regularly exceeds 30°C, keep the pen in a cool cupboard or bag rather than on a shelf.
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.
Practical Tips For Mounjaro Storage At Home
Store your opened Mounjaro pen in a cool, dark place—a cupboard or drawer works well. Never leave it in the bathroom (humidity can affect it) or in direct sunlight. If you travel, use an insulated bag or cool pouch to maintain the correct temperature if you'll be away from home for several hours. Use our free GLP-1 weight loss calculator above to track your projected results as you continue your Mounjaro dose titration schedule. Keep your prescription records accessible—your GP or prescriber may need to confirm your storage conditions if any issues arise with your injections.
- 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 long after opening Mounjaro can I keep it at room temperature?
Once you inject your first dose, you can keep the KwikPen at room temperature (below 30°C) for exactly 30 days. After 30 days, you must dispose of the pen safely, even if doses remain. Always mark the first-use date on the carton.
What happens if Mounjaro accidentally gets too warm?
If your Mounjaro pen is exposed to temperatures above 30°C for extended periods, the medication may be compromised. Do not use it. If unsure, contact your prescriber or pharmacist for advice. Always store below 30°C when out of the fridge.
Can I travel with Mounjaro without a fridge?
Yes. For journeys up to a few hours, you can carry an unopened or opened pen at room temperature. For longer trips, use an insulated travel bag or cool pouch. Never expose Mounjaro to direct sunlight or extreme heat, especially in cars.
Is Mounjaro the same as other tirzepatide injections?
Mounjaro is the brand name for tirzepatide—the only prescription tirzepatide product currently available in the UK for weight management. It works as a dual GIP and GLP-1 receptor agonist, unlike Wegovy (semaglutide), which is a GLP-1-only medication.
What should I do if I accidentally froze my Mounjaro pen?
Do not use a frozen Mounjaro pen. Contact your prescriber or pharmacist immediately to request a replacement. Freezing can damage the medication, making it unsafe or ineffective for your weight management treatment.
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.