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 3 Month Supply in the UK
A 3 month supply of Mounjaro in the UK typically consists of 12 individual KwikPen injection devices — enough for one injection per week over 12 weeks. Each KwikPen contains a single pre-filled dose and comes in strengths ranging from 2.5 mg to 15 mg, depending on your personalised treatment plan. Understanding how Mounjaro supplies work, how to store them, and what to expect in terms of cost and access is essential if you're considering this prescription weight loss injection or already taking it. This guide covers everything you need to know about obtaining and managing a 3 month supply of tirzepatide (Mounjaro) in the UK.
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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.
How Mounjaro Supplies Work in the UK
Mounjaro is a prescription-only weight loss injection that comes in pre-filled KwikPen devices. Each pen delivers exactly one dose and is designed for single use — you cannot refill or reuse a KwikPen. For a 3 month supply, you'll receive 12 separate pens (one injection per week for 12 weeks). The dose you receive depends on your personalised treatment plan, which typically starts at 2.5 mg and increases gradually over weeks or months during the dose titration phase.
Your prescription will specify your exact dose schedule. Common titration patterns include:
- Weeks 1–4: 2.5 mg (one pen)
- Weeks 5–8: 5 mg (one pen)
- Weeks 9–12: 7.5 mg or higher (one pen)
This means your 3 month supply may include pens at different strengths if you're still titrating. Once you reach your maintenance dose, all pens will be the same strength. A UK-licensed prescriber will assess your suitability and create your personalised schedule following a clinical assessment.
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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
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Storage, Cost, and NHS vs Private Access
Mounjaro KwikPens must be stored in a refrigerator at 2–8°C until first use — never freeze them. Once you start using a pen, it can be kept at room temperature (below 30°C) for up to 30 days. For a 3 month supply, keep unopened pens refrigerated and rotate opened pens to room temperature as needed each week.
Cost varies significantly: NHS access is through specialist tier 3/4 weight management services (availability varies by region with potential waiting lists), while private prescriptions typically cost £129–£300+ per month depending on dose, with a 3 month supply costing approximately £400–£900. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Always consult your GP or a licensed prescriber to discuss which access route is right for you.
Mounjaro KwikPens must be stored in a refrigerator at 2–8°C until first use — never freeze them. Once you start using a pen, it can be kept at room temperature (below 30°C) for up to 30 days. For a 3 month supply, keep unopened pens refrigerated and rotate opened pens to room temperature as needed each week.
Cost varies significantly: NHS access is through specialist tier 3/4 weight management services (availability varies by region with potential waiting lists), while private prescriptions typically cost £129–£300+ per month depending on dose, with a 3 month supply costing approximately £400–£900. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Always consult your GP or a licensed prescriber to discuss which access route is right for you.
- 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 many pens come in a 3 month Mounjaro supply?
A 3 month supply contains 12 KwikPen devices — one for each week of the 12-week period. Each pen is pre-filled and single-use. If you're still in dose titration, pens may be at different strengths (e.g. some 2.5 mg, some 5 mg). Once at maintenance dose, all pens are identical.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is NICE-approved and available through NHS specialist weight management services (tier 3/4). Access varies significantly by region and ICB, with some areas having long waiting lists. Your GP can refer you to your local specialist service. Private prescriptions are also available through UK-licensed online prescribers.
How much does a 3 month Mounjaro supply cost in the UK?
Private costs typically range from £400–£900 for a 3 month supply, depending on your dose (higher doses are more expensive). NHS access is free but subject to regional availability and referral criteria. Prices vary between private prescribing services — always compare.
How should I store my 3 month Mounjaro supply?
Keep unopened KwikPens refrigerated at 2–8°C. Do not freeze. Once you open a pen for first use, it can be stored at room temperature (below 30°C) for up to 30 days. Dispose of used pens in a sharps bin or as directed by your pharmacy.
Is Mounjaro the same as Wegovy?
No. Both are prescription weight loss injections, but Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro achieved slightly higher average weight loss (~20.9% vs ~14.9%), but individual results vary. Both require prescription and clinical assessment.
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.