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 Buy Tirzepatide in the UK
Tirzepatide, the active ingredient in Mounjaro, is available in the UK through two main routes: NHS specialist weight management services and private online prescribing. Access depends on your eligibility, health conditions, and preferred pathway. The NHS provides tirzepatide through tier 3 services, while private prescribing offers faster access without referral. Both routes require a clinical assessment and prescription from a UK-licensed healthcare professional. This guide explains your options.
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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 Access to Tirzepatide in the UK
NHS tirzepatide prescribing is available through specialist weight management services (tier 3 and tier 4). You cannot get tirzepatide directly from your GP — you must be referred to a dedicated weight management service.
- Eligibility: BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea)
- Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage — eligibility may start at BMI 27.5
- Referral process: Ask your GP to refer you to your local NHS weight management service
- Assessment: You'll be assessed by a specialist team including doctors, dietitians, and behavioural specialists
- Availability: Varies significantly by region (Integrated Care Board). Some areas have long waiting lists; others may have limited availability
NICE has approved tirzepatide for use within NHS specialist weight management services as part of a comprehensive treatment programme alongside dietary and lifestyle support.
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.
Private Tirzepatide Prescribing in the UK
Private access to tirzepatide is available through GPhC-registered online pharmacies and prescribing services. You can obtain a prescription without NHS referral or waiting lists.
- Online assessment: Complete a health questionnaire reviewed by a UK-licensed prescriber
- Prescription issued: If clinically appropriate, a prescription is issued and dispensed by a registered pharmacy
- Cost: Typically £129–£280 per month depending on dose (2.5 mg to 15 mg weekly)
- Speed: Often receive your first dose within 1–2 weeks
- Flexibility: Can adjust doses and manage your treatment more independently than NHS routes
Private prescribing requires a legitimate clinical assessment — it's not a direct purchase. A licensed prescriber must determine that tirzepatide is safe and appropriate for you based on your health history.
- 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 tirzepatide over the counter in the UK?
No. Tirzepatide is prescription-only in the UK and cannot be purchased without a prescription from a licensed healthcare professional. It's not available in pharmacies without a valid prescription.
What's the difference between NHS and private tirzepatide prescribing?
NHS access is through specialist weight management services (tier 3) — free but often involves referral and waiting lists. Private prescribing is faster and doesn't require NHS referral, but costs £129–£280 per month. Both require clinical assessment and a valid prescription.
How long does it take to get tirzepatide on the NHS?
Waiting times vary significantly by region. Some NHS weight management services have waiting lists of 6–12 months or longer. Private prescribing typically takes 1–2 weeks from assessment to receiving your first dose.
What's the maximum dose of tirzepatide available in the UK?
The maximum licensed dose is 15 mg once weekly. Most people start at 2.5 mg and increase gradually — typically by 2.5 mg every 4 weeks — until reaching an effective maintenance dose.
Do I need a specific health condition to get tirzepatide on the NHS?
Not always. You're eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related condition like type 2 diabetes, high blood pressure, or cardiovascular disease. Your GP and specialist team will assess 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.