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 Once Opened — Storage, Cost & Access in the UK
Once you've opened your Mounjaro KwikPen, it can be stored at room temperature for up to 30 days before it must be disposed of. Understanding storage requirements, costs, and how to access tirzepatide in the UK is essential for anyone considering this prescription-only weight management injection. This guide covers private costs, NHS access routes, and what to expect from the prescription process in the UK.
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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 Cost and Access in the UK
In the UK, Mounjaro (tirzepatide) is available through two main routes: NHS specialist weight management services or private online prescription. Private costs typically range from £129 to £320 per month depending on your dose, with the lowest doses (2.5mg and 5mg) generally costing less than higher maintenance doses (10mg to 15mg). Each KwikPen contains four weekly doses, so costs reflect a full month's treatment. NHS access through NICE-approved specialist tier 3 services is free, but availability varies significantly by region and waiting lists can be lengthy—some areas report waiting 6–12 months or longer for initial assessment.
- Private prescription: £129–£320/month depending on dose
- Each KwikPen = 4 weeks' supply (4 injections)
- NHS route: free but subject to regional availability and waiting lists
- Eligibility assessed individually by a prescriber
- Costs do not include GP consultations if using private route
When comparing Mounjaro vs Wegovy costs, tirzepatide pricing is typically similar to semaglutide, though this varies between providers. The dual GIP/GLP-1 mechanism of tirzepatide may offer different results than GLP-1-only medications—clinical trials showed average weight loss of 15–21% with Mounjaro, though individual outcomes vary considerably.
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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 Access Mounjaro Once You've Started Treatment
If you're already taking Mounjaro through a private prescription, your prescriber will typically arrange repeat dispensing through a GPhC-registered pharmacy. Once opened, store your pen at room temperature (below 30°C) for up to 30 days—do not refrigerate after opening. After 30 days, dispose of the pen safely even if medication remains. For NHS patients, repeat prescriptions are managed through your specialist weight management service. Ensure you have a plan in place for dose titration (gradual increase) and ongoing monitoring, as Mounjaro eligibility in the UK requires assessment of BMI and weight-related health conditions.
- Opened pens: room temperature storage up to 30 days
- Unopened pens: refrigerate at 2–8°C until first use
- Set up repeat dispensing before your current pen runs out
- Track injection dates to avoid missed 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.
How much does Mounjaro cost privately in the UK per month?
Private Mounjaro costs range from approximately £129–£320 per month depending on your dose and provider. Starter and low doses (2.5mg and 5mg) are usually cheaper than higher maintenance doses (10–15mg). Each KwikPen contains four weekly injections, so monthly cost covers a full 4-week supply. Prices vary between registered online prescription providers, so it's worth comparing.
Can I get Mounjaro free on the NHS?
Yes, Mounjaro is available free through NICE-approved NHS specialist weight management services (tier 3). However, you need a GP referral and availability varies significantly by region. Some areas have lengthy waiting lists—6–12 months or longer. Your GP can advise whether you meet NHS eligibility criteria and refer you to your local service if available.
How long does Mounjaro last once the KwikPen is opened?
Once opened, Mounjaro can be stored at room temperature (below 30°C) for up to 30 days. After 30 days, the pen must be disposed of safely even if medication remains. Unopened pens should be refrigerated at 2–8°C and can be used until their expiry date. Mark your opening date on the pen to track this accurately.
What's the difference between Mounjaro and Wegovy costs in the UK?
Private costs for Mounjaro and Wegovy (semaglutide) are typically similar—both ranging from £129–£320 monthly depending on dose and provider. However, Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1-only, which may affect individual weight loss outcomes. Clinical trials showed slightly higher average weight loss with Mounjaro, though results vary significantly between individuals.
Do I need a GP referral to get private Mounjaro?
No, you don't need a GP referral for private Mounjaro. You can access it through a private online consultation with a UK-licensed prescriber via GPhC-registered pharmacies. A clinical assessment is required to ensure the medication is appropriate for you. If you're pursuing NHS access, a GP referral to a specialist weight management service is necessary.
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.