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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How to Order Mounjaro in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK, but you cannot simply order it online without a clinical assessment. To obtain Mounjaro, you must first have a prescription from a UK-licensed prescriber, which requires an evaluation of your eligibility based on your BMI, health conditions, and medical history. Access is available through both NHS specialist weight management services and private online prescribing clinics, each with different pathways, timescales, and costs. This guide explains how the ordering process works in the UK.
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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.
NHS vs Private Access Routes
NHS Access: NICE has approved tirzepatide (Mounjaro) within NHS specialist tier 3 weight management services. To access it through the NHS, you must be referred by your GP to your local integrated care board (ICB) specialist weight management service. Availability varies significantly by region — some areas have waiting lists of several months or longer. Once referred, a multidisciplinary team will assess your eligibility, which includes BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds (27.5 kg/m² or above).
Private Access: Through GPhC-registered online clinics, Mounjaro is available without NHS referral. A licensed prescriber conducts an online clinical assessment, and if suitable, issues a prescription that is dispensed by a registered pharmacy. This route is faster (typically within days) but involves costs ranging from approximately £150–£250 per month depending on dose.
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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.
Before You Order — Eligibility and Assessment
Before ordering Mounjaro, you must meet eligibility criteria. You need a BMI of 30 or above, or 27–29.9 with weight-related health conditions including type 2 diabetes, prediabetes, high blood pressure, high cholesterol, or sleep apnoea. You cannot take Mounjaro if you are under 18, pregnant, breastfeeding, have a personal or family history of thyroid cancer, or are allergic to tirzepatide. A prescriber will also review your current medications — Mounjaro may affect the absorption of oral contraceptives and other oral medications. Use our free BMI calculator above to check your starting point, and consult your GP or a licensed prescriber about your individual eligibility and suitability for this medication.
- 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.
Can I buy Mounjaro online without a prescription in the UK?
No. Mounjaro is prescription-only in the UK. Any online clinic must issue a valid prescription from a UK-licensed prescriber following a clinical assessment. Be cautious of websites claiming to sell Mounjaro without a prescription — these are not legitimate. Always use GPhC-registered pharmacies.
How long does it take to get a Mounjaro prescription through the NHS?
NHS timescales vary significantly by region. Initial GP referral to a specialist weight management service may take weeks, and then the specialist service waiting list can be several months in some areas. Private routes are typically faster (days to weeks), but involve costs.
What happens during the online prescription assessment for private Mounjaro?
A UK-licensed prescriber will ask about your weight, height, BMI, medical history, current medications, and weight-related conditions. They may also ask about your diet and exercise habits. Based on this assessment, they will decide if Mounjaro is suitable. If approved, a prescription is issued and sent to a registered pharmacy.
Does the Mounjaro KwikPen come ready to use when I order it?
Yes. Each Mounjaro KwikPen arrives pre-filled with a single dose and is ready to inject. You do not need to mix or prepare the medication. Full instructions are provided, and you can also ask your prescriber or pharmacist for injection guidance.
What's the difference between ordering Mounjaro and Wegovy in the UK?
Both are once-weekly injections for weight management, but Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed different average weight loss outcomes — Mounjaro averaged 15–clinically studied weight loss, while Wegovy averaged approximately 15%. Eligibility and pricing may differ. Compare using our GLP-1 weight loss calculator to understand projected outcomes at different doses.
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.