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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How to Keep Mounjaro in the Fridge — UK Storage Guide
Mounjaro (tirzepatide) is a prescription-only weight management injection that must be stored correctly to remain effective. In the UK, unopened Mounjaro KwikPen devices should be kept in the fridge at 2°C to 8°C until you're ready to use them. Proper storage protects the medication and ensures it works as intended when prescribed by your GP or through a licensed UK prescriber. This guide explains exactly how to store your Mounjaro safely at home.
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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 Fridge Storage Requirements
Unopened Mounjaro pens must be stored in a refrigerator between 2°C and 8°C. Keep them in their original carton to protect from light exposure. Do not freeze your Mounjaro — if a pen has been frozen, it should not be used. The medication will remain safe to use until the expiry date printed on the carton, provided it has been continuously refrigerated.
After you have taken your first injection from a KwikPen:
- The pen can be stored at room temperature (below 30°C) for up to 30 days
- You must discard the pen 30 days after first use, even if medication remains
- Keep it away from direct heat and sunlight during this period
- Do not return it to the fridge once you have started using it
Each KwikPen contains 4 doses (4 weeks' supply). If you need to dispose of your Mounjaro, ask your pharmacist or GP about the correct disposal route — do not put it in household waste or down the drain.
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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.
NHS Prescribing and Dose Titration
Mounjaro is available through NHS specialist weight management services (tier 3) and via private prescribing from UK-licensed providers. If your GP refers you to an NHS tier 3 service, they will manage your dose titration — the gradual increase from 2.5 mg up to your maintenance dose over 16–20 weeks. You'll need to keep each pen refrigerated until the week you use it. Storage matters because tirzepatide is sensitive to temperature; improper storage reduces its effectiveness. Our GLP-1 weight loss calculator can help you understand projected results across different doses once your prescriber has established your optimal treatment plan.
- 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 store Mounjaro in the door of my fridge?
Yes, the fridge door is acceptable as long as the temperature stays between 2°C and 8°C. However, the main body of the fridge is more stable. Avoid storing Mounjaro in the coldest part (at the back against the wall), as temperatures can dip below 0°C and freeze the medication.
What happens if Mounjaro freezes?
If your Mounjaro has been frozen, do not use it. Freezing damages the medication and makes it unsafe and ineffective. If you suspect freezing, check the carton for ice crystals. When in doubt, contact your prescriber or pharmacist for guidance.
How long can Mounjaro stay out of the fridge?
Once you start using a KwikPen, it can stay at room temperature (below 30°C) for up to 30 days. After 30 days from first use, you must discard it. Unopened pens must always be refrigerated.
Do I need to bring my Mounjaro pen to room temperature before injecting?
No, you can inject directly from the fridge. Some people find a cold injection slightly uncomfortable, so you may choose to remove the pen 15–30 minutes before use to warm it naturally. Never heat it deliberately with hot water or a heat source.
Can I share my Mounjaro fridge space with food?
Yes. Mounjaro is safe to store alongside food in a standard fridge. Keep it in its original carton for protection. Label it clearly, especially if others use the same fridge, and explain it is prescription medication.
Ready to take control of your weight loss journey?
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