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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Mounjaro Storage Temperature vs Wegovy
Both Mounjaro and Wegovy require careful storage to maintain their effectiveness, but the storage requirements are identical. Both injections must be kept refrigerated at 2°C to 8°C in unopened pens and can be stored at room temperature (below 30°C) for up to 30 days after first use. Understanding how to store your weight loss injection correctly is essential for safe and effective treatment. This guide explains storage temperature requirements for both medications and what to do if storage guidelines are not followed.
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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.
Storage Temperature Requirements for Both Medications
Unopened pens: Both Mounjaro (tirzepatide) and Wegovy (semaglutide) must be stored in a refrigerator between 2°C and 8°C until first use. Keep pens in their original carton to protect them from light. Do not freeze either medication — if frozen, they cannot be used and must be disposed of safely. Check the expiry date on the carton; unopened pens can be used until this date if stored correctly in the fridge.
- Refrigerator temperature: 2°C to 8°C (standard fridge setting)
- Keep in original carton to protect from light
- Never freeze — frozen pens must be discarded
- Check expiry date before use
After first use: Once you have opened a pen and given yourself your first injection, you can store it at room temperature below 30°C for up to 30 days. After 30 days, even if it appears unchanged, the pen must be disposed of safely. Both Mounjaro and Wegovy follow these identical post-use storage rules.
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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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Why Storage Matters and Clinical Differences
Storing these injections correctly preserves the active ingredient and ensures the medication works as intended. Although Mounjaro and Wegovy have identical storage temperature requirements, they differ in their mechanism of action. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1 receptor agonist only. This difference affects how they work in your body, not how you store them. Your prescriber will decide which medication is suitable for you based on your individual health profile, eligibility, and clinical assessment. Both are prescription-only medicines available through NHS specialist weight management services or private online prescribing in the UK.
- 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 or Wegovy in a standard fridge?
Yes, both medications are stored in a standard household fridge at 2°C to 8°C. This is the normal temperature range for a kitchen refrigerator. Keep the pens in their original carton to protect them from light damage. Never store them in the freezer compartment.
What happens if Mounjaro or Wegovy gets frozen?
If either medication is accidentally frozen, it cannot be used and must be disposed of safely. Freezing damages the active ingredient. Do not attempt to thaw and use frozen pens. Contact your prescriber or pharmacist for guidance on safe disposal and obtaining a replacement.
How long can I keep Mounjaro or Wegovy at room temperature?
Both medications can be kept at room temperature (below 30°C) for up to 30 days after your first injection. After 30 days, the pen must be discarded, even if medication remains inside. Keep track of your opening date using the label on the KwikPen.
Is there any storage difference between Mounjaro and Wegovy?
No, storage requirements are identical for both medications. Both use the same 2°C to 8°C refrigeration before use and 30-day room temperature storage after opening. The only differences are in their mechanism of action and dose ranges, not storage or handling.
Can I travel with Mounjaro or Wegovy?
Yes, you can travel with unopened pens in a cool bag with an ice pack to maintain 2°C to 8°C temperature. Once opened, you have 30 days to use the pen at room temperature, making short trips easier. For longer trips, ask your prescriber about your injection schedule and storage options.
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