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 Ingredients and How to Access It in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. The active ingredient is tirzepatide, a dual GIP and GLP-1 receptor agonist that works differently from other weight loss medications like Wegovy. Understanding what's in Mounjaro, how much it costs, and your access options helps you make informed decisions about whether this treatment is right for you. This guide covers the active ingredient, UK prescription costs, and both NHS and private routes to access.
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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.
Active Ingredient and What Mounjaro Contains
Tirzepatide is the active pharmaceutical ingredient in Mounjaro. It's a synthetic peptide that activates two natural hormone pathways in your body: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual mechanism is what distinguishes Mounjaro from other weight loss injections. Each Mounjaro KwikPen contains one of five available doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg of tirzepatide. The inactive ingredients include sodium phosphate dibasic dihydrate, sodium dihydrogen phosphate dihydrate, sodium chloride, and water for injection. Mounjaro is manufactured by Eli Lilly and Company and is subject to additional MHRA monitoring (Black Triangle ▼ status). The dose titration schedule means you start at 2.5 mg and typically increase every 4 weeks to find your optimal maintenance dose, with a maximum of 15 mg once weekly.
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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.
Mounjaro Cost and Access Routes in the UK
Private access: Mounjaro is available through private online consultations with UK-licensed prescribers, typically costing between £129–£300+ per month depending on your dose and provider. A clinical assessment is required before a prescription is issued. NHS access: NICE has approved tirzepatide for use within NHS specialist weight management services (tier 3/4). Access is through referral from your GP, though availability and waiting times vary significantly by region. Many ICBs have extended waiting lists. Use our free BMI calculator above to check your current BMI category and understand your eligibility for treatment. Our GLP-1 weight loss calculator can help you estimate potential outcomes with Mounjaro at different 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.
What is the active ingredient in Mounjaro?
Tirzepatide is the active ingredient in Mounjaro. It's a dual GIP and GLP-1 receptor agonist that works on two natural hormone pathways to help reduce appetite and support weight management. This dual mechanism makes it different from single-action GLP-1 medications like Wegovy.
How much does Mounjaro cost on private prescription in the UK?
Private Mounjaro costs typically range from £129–£300+ per month depending on your dose and the private provider. Exact pricing varies by clinic. You'll need an online clinical assessment before prescription, and costs increase at higher doses (5 mg through to 15 mg maximum).
Can I get Mounjaro on the NHS?
Yes, NICE has approved tirzepatide for NHS specialist weight management services. You'll need a GP referral to a tier 3 or 4 weight management service. Availability varies by region, and waiting lists can be several months to over a year in some areas.
What's the difference between Mounjaro and Wegovy in terms of active ingredients?
Mounjaro contains tirzepatide (dual GIP+GLP-1 agonist), while Wegovy contains semaglutide (GLP-1 agonist only). The dual mechanism of Mounjaro may produce different results compared to Wegovy, though individual responses vary significantly.
Do I need a prescription to buy Mounjaro in the UK?
Yes, Mounjaro is prescription-only. You cannot buy it over the counter. You'll need a prescription from a UK-licensed GP or prescriber following a clinical assessment that confirms you're eligible and it's safe for you.
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.