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
Do You Have To Keep Mounjaro Refrigerated?
Yes, unopened Mounjaro KwikPen devices must be kept refrigerated at 2–8°C (36–46°F) until first use. However, once you start using a pen, you can store it at room temperature below 30°C for up to 30 days. Proper storage is essential to maintain the medication's effectiveness and safety. This guide explains Mounjaro storage requirements in the UK and what you need to know before starting this prescription weight management injection.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Requirements and Access in the UK
Unopened Mounjaro pens: Store in a refrigerator at 2–8°C. Keep in the original carton to protect from light. Do not freeze — if a pen freezes, you cannot use it. Unopened pens can be used until the expiry date printed on the carton if kept refrigerated properly.
After starting a pen: Once you inject your first dose, the pen can be stored at room temperature (below 30°C) for up to 30 days. After 30 days, dispose of the pen even if medication remains inside. Keep away from heat and direct sunlight during room temperature storage.
Mounjaro is a prescription-only tirzepatide injection, available in the UK through NHS specialist weight management services or private online prescribing following clinical assessment. Access to Mounjaro on the NHS typically requires referral to a tier 3 specialist weight management service, though availability varies significantly by region and ICB.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Mounjaro Cost and Private Prescription Access in the UK
Private Mounjaro prescriptions in the UK typically cost between £129–£320 per month depending on dose and supplier, with lower starting doses (2.5 mg) at the cheaper end and higher maintenance doses (15 mg) costing more. This compares to Wegovy, another once-weekly GLP-1 injection, which costs roughly £150–£300 monthly. Private prescriptions are issued by UK-licensed prescribers following an online consultation and clinical assessment, then dispensed by GPhC-registered pharmacies without requiring NHS referral.
NHS access involves a waiting period that can extend several months in many regions, making private options more accessible if you meet eligibility criteria. Both routes require assessment of your BMI (typically 30+, or 27+ with weight-related health conditions) and medical history. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to see projected results at different Mounjaro doses.
- 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 fridge door?
No. Store unopened Mounjaro in the main refrigerator compartment at 2–8°C, not in the door where temperature fluctuates. Keep the pen in its original carton to protect from light. Temperature consistency is important for medication stability.
What happens if Mounjaro freezes?
Do not use a frozen Mounjaro pen — freezing damages the medication and makes it unsafe. If your pen has frozen, contact your prescriber or pharmacist for advice. Store your pens away from freezer compartments.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs roughly £129–£320 per month depending on dose (2.5 mg to 15 mg). Prices vary slightly between providers. Each KwikPen contains 4 weeks of doses. NHS access is free but often has longer waiting times.
How do I get a private Mounjaro prescription in the UK?
Complete an online consultation with a UK-licensed prescriber, usually through a GPhC-registered pharmacy or online clinic. The prescriber assesses your BMI, medical history, and eligibility. If approved, a prescription is issued and medication is dispensed by post or collection.
Is Mounjaro cheaper on the NHS or privately?
NHS Mounjaro is free at point of use, but access requires referral to specialist services with potential waiting lists. Private prescriptions cost £129–£320/month but are available immediately after clinical assessment. Your choice depends on cost tolerance and urgency.
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.