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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What Temperature Should Mounjaro Be Stored At?
Mounjaro (tirzepatide) is a prescription-only injection that requires careful storage to remain effective. Unopened Mounjaro KwikPens must be stored in a refrigerator at 2°C to 8°C until you're ready to use them. Once you start using a pen, you can keep it at room temperature below 30°C for up to 30 days. Understanding proper storage is essential for maintaining the medication's effectiveness and getting the most from your treatment. This guide covers everything UK patients need to know about storing Mounjaro safely.
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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 Storage Temperature: Complete Guidelines
Unopened Mounjaro pens must be stored in a refrigerator between 2°C and 8°C. This is typically the standard fridge temperature in UK homes. Each KwikPen contains four weekly doses, so one pen lasts four weeks. Keep pens in their original carton to protect them from light exposure. If a pen freezes, do not use it — frozen Mounjaro cannot be safely administered. Pens can be stored at refrigerator temperature until the expiry date printed on the carton.
After your first injection, you can store the same KwikPen at room temperature below 30°C for a maximum of 30 days. This makes it convenient to carry in a bag or keep in your kitchen. However, once 30 days have passed since first use, you must dispose of the pen safely, even if there are remaining doses. Do not return pens to the fridge after they've been at room temperature, as temperature fluctuations can affect the medication.
- Storage temperature: 2–8°C (unopened) or below 30°C (after first use)
- Duration at room temperature: maximum 30 days after first injection
- Keep away from heat sources and direct sunlight
- Dispose of used pens in a yellow sharps bin or as directed by your pharmacy
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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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Accessing Mounjaro in the UK: NHS vs Private Routes
In the UK, Mounjaro (tirzepatide) can be accessed through two main routes. The NHS route involves referral to a specialist tier 3 or tier 4 weight management service from your GP. NICE has approved tirzepatide for NHS use, but availability varies significantly by region and waiting lists can extend several months in many areas. The private route involves an online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. Once clinically assessed and approved, Mounjaro is dispensed and delivered to your home with proper storage instructions included. Online consultations typically cost £20–£50 and medication costs vary by dose, ranging roughly £140–£250 per month at higher maintenance doses.
- NHS access: free but may involve waiting lists; varies by region
- Private access: faster; requires online clinical assessment and ongoing prescription costs
- Always store according to guidelines regardless of access route
- 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 keep Mounjaro in a regular kitchen fridge?
Yes. A standard UK domestic fridge maintains 2–8°C, which is the correct storage temperature for unopened Mounjaro KwikPens. Keep pens in their original carton to protect from light. Ensure your fridge doesn't freeze items — if Mounjaro freezes, it must be discarded.
What happens if Mounjaro gets too warm?
If unopened pens are exposed to temperatures above 8°C for extended periods, the medication's stability may be compromised and you should not use them. Once opened, you have 30 days at room temperature below 30°C. Beyond that, discard the pen safely.
How do I dispose of Mounjaro pens safely?
Used Mounjaro KwikPens contain needles and must go in a yellow sharps bin, not household recycling or general waste. Ask your pharmacy for a sharps bin if you don't have one, or return used pens to the pharmacy for safe disposal.
Can I travel with Mounjaro and keep it cool?
Yes. You can carry an in-use Mounjaro KwikPen at room temperature (below 30°C) for up to 30 days. For longer trips, use a cooling pouch or medication travel case with ice packs to maintain 2–8°C. Check airline rules before flying with injectable medication.
How does Mounjaro storage compare to Wegovy?
Both Mounjaro and Wegovy require identical storage: 2–8°C unopened, or below 30°C after first use for up to 30 days. Both medications come in pre-filled pens designed for once-weekly injection. Always follow the specific storage instructions provided with your prescription.
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.