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 Or Ozempic For Weight Loss — What's The Difference?
Many people searching for prescription weight loss treatment in the UK encounter both Mounjaro and Ozempic, often confused about which is which. The key difference is their approval and purpose: Mounjaro (tirzepatide) is specifically licensed for weight management in the UK, whilst Ozempic (semaglutide 1 mg) is approved for type 2 diabetes only. Using Ozempic for weight loss would be off-label and not recommended. If you're considering a weekly weight loss injection, Mounjaro or Wegovy (semaglutide 2.4 mg, the licensed weight loss version) are your prescription options. This guide explains the differences, costs, and how to access treatment.
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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.
Mounjaro Vs Ozempic — The Critical Difference
Mounjaro (tirzepatide) is licensed in the UK specifically for weight management. It's a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to help regulate appetite and support feeling fuller after meals. Clinical trials showed Mounjaro helped participants lose an average of 15–21% of body weight at the maximum dose.
Ozempic (semaglutide 1 mg) is licensed in the UK for type 2 diabetes management only, not for weight loss. Some people use Ozempic off-label for weight loss, but this is not recommended or supported by UK prescribing guidance. The weight loss version of semaglutide is called Wegovy (2.4 mg), which is the licensed UK weight loss alternative.
- Mounjaro: dual mechanism, licensed for weight management, doses up to 15 mg
- Ozempic: diabetes-only approval, lower dose, not licensed for weight loss
- Wegovy: licensed weight loss alternative with single GLP-1 mechanism, up to 2.4 mg
If your GP or prescriber suggests using Ozempic for weight loss, ask about Mounjaro or Wegovy instead, which are the approved options 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.
Cost And How To Access Mounjaro In The UK
NHS access: Mounjaro is available through NHS tier 3 specialist weight management services following a clinical assessment. Regional availability varies significantly, and waiting lists can be lengthy. You'll need a GP referral to a specialist service in your area.
Private access: Mounjaro is available through private online prescribing following a clinical consultation. Costs typically range from £129 to £320+ per month depending on the dose. Each KwikPen contains 4 weeks of treatment (4 injections). A prescriber will assess your suitability after reviewing your medical history. Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and use our BMI calculator to check your starting point.
Private routes do not require an NHS referral and treatment can often begin more quickly than NHS pathways, though cost is a factor for many patients.
Online private prescription consultations are conducted via secure telehealth platforms. You'll answer questions about your weight, height, medical history, current medications, and weight loss goals. A UK-licensed prescriber reviews your details and decides whether Mounjaro is clinically suitable for you. If approved, a prescription is issued to a GPhC-registered pharmacy, and Mounjaro is dispensed and delivered to your home. Payment is made directly to the private provider — not through the NHS. Always ensure the prescriber and pharmacy are UK-regulated and legitimate before proceeding.
- 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 Ozempic ever prescribed for weight loss in the UK?
Ozempic (semaglutide 1 mg) is licensed for type 2 diabetes only. Some people use it off-label for weight loss, but UK prescribing guidelines do not support this. Mounjaro or Wegovy are the licensed weight loss options. Always discuss options with your GP or prescriber.
What's the difference between Wegovy and Mounjaro?
Both are licensed for UK weight loss, but Mounjaro (tirzepatide) uses a dual GIP+GLP-1 mechanism, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro goes up to 15 mg weekly; Wegovy up to 2.4 mg weekly. Clinical trials showed slightly higher average weight loss with Mounjaro, though results vary individually.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129 to £320+ per month depending on the dose and provider. Each KwikPen contains 4 weekly injections. Prices vary between providers, so it's worth comparing. Always use a GPhC-registered pharmacy to ensure safety and legitimacy.
How long does it take to get Mounjaro on the NHS?
NHS access requires referral to a tier 3 specialist weight management service and clinical assessment. Waiting times vary significantly by region (ICB area), ranging from weeks to over a year in some areas. Private routes often offer faster access but at personal cost.
Do I need a prescription to buy Mounjaro in the UK?
Yes, Mounjaro is prescription-only. You cannot buy it without a valid prescription from a UK-licensed prescriber. Online private prescribers can issue prescriptions following a clinical consultation, but this is not the same as buying over-the-counter medication.
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.