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
Should Mounjaro Be Kept in the Fridge?
Yes, unopened Mounjaro KwikPen must be stored in a refrigerator at 2°C to 8°C before you use it for the first time. Once you've started using a pen, you can keep it at room temperature (below 30°C) for up to 30 days. This matters because proper storage keeps tirzepatide stable and effective. Understanding the correct storage temperature ensures your prescription weight loss medication remains safe and works as intended when you use it.
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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 Temperature and Shelf Life
Unopened Mounjaro pens must be refrigerated:
- Store at 2°C to 8°C (standard fridge temperature)
- Keep in original carton to protect from light
- Can be used until the expiry date printed on the box if kept refrigerated
- Never freeze — if a pen freezes, do not use it
After first injection: You can remove the pen from the fridge and store it at room temperature (below 30°C) for up to 30 days. After 30 days from first use, dispose of the pen safely even if it contains remaining doses. This is different from other GLP-1 medications — always check your specific prescription guidance. If you're comparing tirzepatide (Mounjaro) storage with semaglutide (Wegovy), note that Wegovy has the same refrigeration requirements before first use.
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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.
How to Store Your Mounjaro Pen Correctly
Keep your unopened Mounjaro KwikPen in the fridge compartment, not the freezer — even brief freezing can damage the medication. Store it in its original box to shield it from direct light, which can degrade the tirzepatide. If you're travelling, use a cool bag or insulated pouch with ice packs to maintain the correct temperature during your journey. Once you've had your first injection, you can leave the pen on a shelf or in a cupboard as long as it stays below 30°C. Mark the date you first used the pen so you know when the 30-day room temperature window ends. Always check the expiry date and never use a pen after 30 days from first use, even if it still contains medication.
- 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 temperature should Mounjaro be stored at before first use?
Unopened Mounjaro must be kept in a refrigerator at 2°C to 8°C. This is standard fridge temperature. Keep the pen in its original carton to protect it from light. Do not freeze it under any circumstances — frozen Mounjaro should not be used.
Can I keep my Mounjaro pen at room temperature after I start using it?
Yes. After your first injection, Mounjaro can be stored at room temperature (below 30°C) for up to 30 days. After 30 days, dispose of the pen safely. This applies whether you've used all doses or not.
What happens if my Mounjaro pen freezes accidentally?
Do not use a frozen Mounjaro pen. Freezing damages the tirzepatide medication. If your pen has been frozen, dispose of it and contact your prescriber to arrange a replacement.
How long can unopened Mounjaro stay in the fridge?
Unopened Mounjaro can remain in the fridge until the expiry date printed on the box. As long as you keep it refrigerated at 2°C to 8°C and in the original carton, it will remain stable and safe to use.
Is Mounjaro storage different from Wegovy storage?
Both Mounjaro and Wegovy require refrigeration before first use at 2°C to 8°C. However, storage requirements after first use may differ slightly — always follow the specific guidance on your prescription label or ask your pharmacist to confirm the exact storage instructions for your medication. ``` --- ## CONTEXT & NOTES **Content delivery:** - Direct answer to the primary keyword in the H1 and opening sentence - Semantic keywords naturally woven: "mounjaro kwikpen" (intro, section 2), "tirzepatide" (intro, section 2), "mounjaro vs wegovy" (FAQ Q5), "mounjaro uk prescription" (intro context) - Practical, actionable storage guidance with temperature specifics - Clear distinction between unopened and post-first-use storage - Safety emphasis (freezing risk, disposal timeline) - FAQ covers common user questions without being repetitive **Tool references:** - BMI calculator and GLP-1 weight loss calculator not forced here (storage is purely practical/logistical, not weight-related) - Focus kept on storage accuracy rather than diluting with calculator mentions **Compliance:** - No medical advice given — purely informational storage guidance - UK English throughout: "fridge", "GP", NHS context implied - Prescription status reinforced ("on your prescription") - Clear disclaimer in FAQ about checking specific guidance with prescriber - No pharmacy mentions - No assured outcomes — factual storage information only - Acknowledged that "always check your specific prescription guidance" (compliance note)
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.