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
Does Mounjaro Contain Insulin?
No, Mounjaro does not contain insulin. It's a prescription-only injection containing tirzepatide, which works as a dual GIP and GLP-1 receptor agonist — a completely different type of medicine from insulin. This is an important distinction many people ask about. Understanding how Mounjaro actually works, and how it differs from insulin and other weight loss medications like Wegovy, can help you make an informed decision if your GP considers it appropriate for you.
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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.
How Mounjaro Works Without Insulin
Mounjaro (tirzepatide) is not insulin and doesn't replace or contain insulin. Instead, it's a dual receptor agonist that activates two separate hormone pathways in your body: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). Both are natural hormones your gut already produces after eating.
These hormones work by signalling to your brain that you're full, slowing how quickly food leaves your stomach, and helping regulate how your body uses fat and glucose. This dual mechanism is what distinguishes Mounjaro from Wegovy, which activates only the GLP-1 pathway. In the SURMOUNT clinical trials, this dual action supported average weight loss of approximately 15–21% of body weight over 72 weeks — though individual results vary significantly. Mounjaro is given as a once-weekly KwikPen injection, with doses ranging from 2.5 mg to 15 mg depending on individual response and prescriber guidance.
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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 vs Wegovy: Key Differences
While both Mounjaro and Wegovy are prescription-only weight management injections licensed in the UK, they work through different mechanisms. Wegovy (semaglutide) is a GLP-1 only agonist — it activates one pathway. Wegovy clinical trials (STEP-1) showed average weight loss of approximately 15% over 68 weeks at the maximum 2.4 mg dose. Mounjaro's dual GIP+GLP-1 action may offer a different response profile for some people, though results vary individually.
Both require a prescription following clinical assessment and eligibility criteria (BMI 30+ or 27+ with weight-related health conditions). Neither contains insulin. Your prescriber will assess which, if either, is suitable for your individual health profile. Use our free GLP-1 weight loss calculator above to explore potential outcomes, and our BMI calculator to check your starting point for eligibility.
- 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.
Does Mounjaro contain insulin?
No. Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist. It is not insulin and doesn't work like insulin. It's a different class of medication designed to support weight loss by affecting hormones that regulate appetite and fullness.
Why do people confuse Mounjaro with insulin?
Mounjaro is an injection, and many people associate injections with insulin treatment. Additionally, both can be used in weight management contexts. However, the mechanisms are completely different — Mounjaro activates natural hormone pathways, while insulin directly replaces or supplements the hormone your pancreas produces.
Is Mounjaro suitable if I don't have diabetes?
Yes. Mounjaro is licensed for weight management in UK adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions — you don't need diabetes to be eligible. Your GP can assess whether it's appropriate for your individual health profile.
How does Mounjaro compare to Wegovy for weight loss?
Both are licensed for weight management in the UK. Mounjaro showed average weight loss of 15–21% in clinical trials, while Wegovy showed approximately 15%. Individual results vary significantly. Your prescriber will assess which, if either, suits your specific circumstances.
How is Mounjaro prescribed in the UK?
Mounjaro is prescription-only and requires a clinical assessment. You can access it through NHS specialist tier 3 weight management services or through a private online consultation with a UK-licensed prescriber. Either route requires eligibility assessment before dispensing.
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.