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
Is Mounjaro A Long-Acting Insulin?
No, Mounjaro is not insulin. It's a prescription-only injection containing tirzepatide, a dual GIP and GLP-1 receptor agonist. This means it works differently from insulin — it doesn't replace or mimic insulin directly. Instead, Mounjaro helps regulate appetite, reduce cravings, and support weight management in UK adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Understanding what Mounjaro actually is helps clarify how it works and whether it might be suitable for you.
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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.
What Is Mounjaro And How Does It Differ From Insulin?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — not an insulin replacement. Insulin is a hormone that regulates blood sugar directly by helping cells absorb glucose. Mounjaro works through two different pathways: it activates GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptors in the brain and gut.
These pathways help by:
- Reducing appetite and food cravings
- Increasing feelings of fullness after smaller meals
- Slowing how quickly food leaves the stomach
- Supporting natural insulin release in response to food
Unlike long-acting insulin, which is primarily used for type 2 diabetes management, Mounjaro is licensed specifically for weight management. It's available as a pre-filled KwikPen — a once-weekly injection — and requires a prescription following a clinical assessment from a UK-licensed healthcare professional.
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.
Accessing Mounjaro In The UK: NHS And Private Routes
In the UK, you can access Mounjaro through two main routes. The NHS route involves referral to a specialist tier 3 weight management service through your GP. However, availability varies significantly by region, and waiting lists can be very long. The private route involves an online consultation with a UK-licensed prescriber, typically costing between £129–£320 per month depending on your dose and the provider. Both routes require a clinical assessment to confirm you're eligible. Use our free BMI calculator above to check your starting point, then discuss options with your GP or explore private prescribing if you prefer faster access.
- 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.
Is Mounjaro the same as insulin?
No. Mounjaro (tirzepatide) is a GIP/GLP-1 receptor agonist, not insulin. It works through appetite regulation pathways in the brain and gut, whereas insulin directly regulates blood sugar. Both are prescription medications but work very differently and have different uses.
Can people with type 2 diabetes take Mounjaro?
Mounjaro is licensed for weight management, not diabetes treatment. Some people with type 2 diabetes may also have excess weight and be eligible for Mounjaro, but a healthcare professional must assess this individually. Always inform your prescriber of all medical conditions.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP/GLP-1 agonist (maximum 15 mg weekly), while Wegovy is a GLP-1 agonist only (maximum 2.4 mg weekly). Clinical trials showed Mounjaro users lost slightly more weight on average, but both are prescription-only and individual results vary significantly.
How much does Mounjaro cost on the NHS?
Mounjaro is available through NHS specialist weight management services (tier 3), but access depends on your region and local ICB funding. Waiting lists vary. For private prescriptions, costs typically range from £129–£320 monthly depending on dose and provider.
How do I get Mounjaro in the UK?
Ask your GP about referral to specialist weight management services, or pursue private prescribing through an online consultation with a UK-licensed prescriber. Both require clinical assessment. Use our GLP-1 weight loss calculator to understand potential outcomes before starting treatment.
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.