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 Store Mounjaro Safely in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection that requires proper storage to remain effective. Whether you're accessing Mounjaro through NHS specialist services or private prescription, correct storage is essential for maintaining the medicine's potency and ensuring safe use. This guide covers UK storage requirements, temperature guidelines, and what to do if your Mounjaro KwikPen has been stored incorrectly.
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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 Refrigeration
Unopened Mounjaro pens must be stored in a refrigerator at 2°C to 8°C (standard fridge temperature). Keep the pen in its original carton to protect it from light exposure. Unopened pens can be used until the expiry date printed on the packaging if stored correctly in the refrigerator.
Do not freeze your Mounjaro — if a pen has been frozen, it must be discarded and not used, even if it has thawed. Freezing damages the insulin-like formulation and makes it unsafe.
Once you've used a Mounjaro KwikPen for the first time, you can store it at room temperature below 30°C for up to 30 days. After 30 days of room temperature storage, the pen must be discarded safely, even if there is medication remaining.
- Keep away from direct sunlight and heat sources
- Do not store in a car or near radiators
- Protect from extreme temperature fluctuations
Clinically BackedWeight Loss
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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.
Safe Disposal and Storage Mistakes to Avoid
After 30 days of use at room temperature, or if an unopened pen has passed its expiry date, Mounjaro KwikPens must be disposed of safely. Never throw used pens directly in household waste — needles pose a sharps injury risk. Instead, ask your GP surgery, pharmacist, or NHS services where you accessed the prescription for a sharps disposal container.
Common storage errors include leaving pens on kitchen windowsills in sunlight, storing them in car glove boxes during summer, or attempting to use frozen pens. These mistakes reduce effectiveness and may affect safety. Always check the appearance of your medication before injecting — if it looks cloudy, discoloured, or contains particles (it should be clear), do not use it and contact your prescriber or pharmacist for guidance.
- 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 a non-medical fridge with food?
Yes. Standard domestic fridges are suitable. Keep the pen in its original carton to protect from light. Store away from the freezer compartment to prevent accidental freezing. Store below other items so it doesn't get damaged.
What should I do if my Mounjaro has been frozen?
Do not use it. Freezing damages the medication. Dispose of the pen safely through your GP surgery or pharmacy sharps disposal scheme. Contact your prescriber to arrange a replacement pen immediately.
How long can I keep Mounjaro at room temperature after opening?
Up to 30 days after first use. Mark the start date on your pen with a pen. After 30 days, dispose of it safely even if medication remains, as the formulation degrades and safety cannot be assured.
Is it safe to travel with Mounjaro?
Yes. For short trips (under 30 days), you can carry the pen at room temperature in a cool bag or insulated travel case. For longer trips, research fridge access at your destination. Never store in checked luggage where freezing is possible.
What does "do not freeze" mean — can I store Mounjaro near an ice pack?
Keep the pen away from ice packs, freezer compartments, and anything that could freeze it. Room temperature below 30°C is safe. If travelling, use a cool bag with a cloth barrier between the pen and ice packs to maintain cool (not frozen) conditions.
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.