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 GLP-1 the Same As Mounjaro?
GLP-1 and Mounjaro are not the same thing, though the confusion is common. GLP-1 is a natural hormone that regulates appetite and blood sugar. Mounjaro (tirzepatide) is a prescription-only medication that mimics GLP-1's effects — but it's actually a dual GIP and GLP-1 receptor agonist, making it more powerful than medications that only activate GLP-1 alone. Understanding the difference is important when exploring UK weight management options, whether through the NHS or private prescription routes.
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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.
What's the Difference Between GLP-1 and Mounjaro?
GLP-1 (glucagon-like peptide-1) is a hormone your body produces naturally in the gut after eating. It signals fullness to your brain, slows stomach emptying, and helps regulate blood sugar. GLP-1 receptor agonist medications like Wegovy (semaglutide) work by mimicking this single hormone pathway.
Mounjaro (tirzepatide) is different — it's a dual GIP and GLP-1 receptor agonist. This means it activates two hormone pathways simultaneously, not just one. This dual mechanism is why Mounjaro may produce different results than GLP-1-only medications. In clinical trials, Mounjaro showed an average weight loss of 15–21% of body weight depending on the tirzepatide dose used, though individual results vary significantly. Both require a prescription and clinical assessment before access in the UK.
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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 in the UK: NHS vs Private
NHS access: Mounjaro is available through NHS tier 3 specialist weight management services following GP referral. Availability varies significantly by region, and waiting lists can be substantial. NICE has approved tirzepatide for use within the NHS, but access depends on your local commissioning decisions.
Private prescription route: You can obtain a Mounjaro prescription privately through a UK-licensed online prescriber following an online clinical assessment. If approved, the prescription is dispensed by a GPhC-registered pharmacy. This route typically offers faster access than NHS services. Use our free GLP-1 weight loss calculator to explore potential results at different Mounjaro doses and understand what to expect during treatment.
- 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 a GLP-1 medication?
Not exactly. While Mounjaro activates the GLP-1 pathway, it's technically a dual GIP and GLP-1 receptor agonist — it works on two hormone systems, not one. This dual action is what distinguishes it from GLP-1-only medications like Wegovy, potentially offering different weight loss outcomes. Both require prescription and clinical assessment in the UK.
What does GLP-1 medication mean?
GLP-1 medication refers to drugs that activate the GLP-1 hormone pathway to reduce appetite and support weight loss. Examples include Wegovy (semaglutide) and Saxenda (liraglutide). These are prescription-only and work by mimicking a natural gut hormone. Mounjaro is similar in function but uses a dual mechanism instead of GLP-1 alone.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs vary by provider and dose but typically range from £150–£300+ per month. The exact cost depends on which tirzepatide dose you're prescribed (starting at 2.5 mg and titrating up to 15 mg maximum). Prices differ between private prescribers and pharmacies, so it's worth comparing options before starting treatment.
Can I get Mounjaro on the NHS?
Yes, Mounjaro is available through NHS specialist weight management (tier 3) services, but access varies significantly by region. You'll need a GP referral and must meet eligibility criteria (BMI ≥30 or BMI 27–29.9 with weight-related health conditions). NHS waiting lists can be long — some areas have multi-month delays. Private prescription is faster if you meet clinical criteria.
What's the difference between Mounjaro and Wegovy cost-wise?
Both are prescription-only, but costs differ. Wegovy (semaglutide) typically costs £129–£200+ per month privately, while Mounjaro ranges from £150–£300+ depending on dose. NHS access differs too — both require specialist referral, but availability and waiting times vary by region. Your prescriber will advise which is more suitable for your individual circumstances.
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.