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, sold under the brand name Mounjaro, is a prescription-only weight management injection available in the UK through both NHS specialist services and private prescribing routes. If you're considering tirzepatide as a weekly weight loss injection, you'll need a clinical assessment from a UK-licensed prescriber to determine eligibility. This guide explains both pathways, NHS eligibility criteria, and what to expect when accessing this GLP-1 receptor agonist medication 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 Access to Tirzepatide (Mounjaro) in the UK
NHS prescribing of tirzepatide is managed through tier 3 specialist weight management services, not by standard GP prescription. You'll typically need a referral from your GP to access these services, though availability varies significantly by region depending on your Integrated Care Board (ICB).
- Eligibility criteria: BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- Ethnicity considerations: If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds (27.5+) may apply due to higher health risks at lower weights
- Assessment: NHS specialist services will conduct a full health assessment before prescribing
- Waiting times: NHS waiting lists for tier 3 weight management services can be substantial — in some areas, months to over a year
Once approved, tirzepatide is dispensed through NHS pharmacies at no additional cost beyond your standard prescription charge (or free if eligible).
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 Access to Tirzepatide in the UK
If you prefer not to wait for NHS services, tirzepatide is available privately through UK-registered online prescribing services. A licensed prescriber will conduct an online clinical assessment, and if appropriate, issue a prescription that can be dispensed by a GPhC-registered pharmacy.
- No NHS referral needed — direct access following online consultation
- Faster access — typically within days rather than months
- Cost: Private prescriptions range from approximately £150–£350 per month depending on dose and provider
- Prescription requirement: Every dose requires a valid UK prescription — no medication is dispensed without clinical assessment
Use our free BMI calculator above to check your current BMI before your assessment, and try our GLP-1 weight loss calculator to estimate potential outcomes with tirzepatide.
- 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.
What's the difference between Mounjaro and tirzepatide?
Mounjaro is the brand name for tirzepatide. Tirzepatide is the active drug — a dual GIP and GLP-1 receptor agonist that helps regulate appetite and support weight loss. You may hear both terms used interchangeably, but they refer to the same medication.
Can my GP prescribe tirzepatide directly?
In most cases, no. Tirzepatide prescribing through the NHS is managed by specialist tier 3 weight management services, not by standard GP practice. Your GP can refer you to these services, but cannot typically prescribe tirzepatide directly. Private prescribers can issue prescriptions without NHS referral.
How much does tirzepatide cost privately in the UK?
Private tirzepatide costs typically range from £150–£350 per month depending on the dose (2.5 mg to 15 mg weekly) and the prescribing service. Initial consultations may be additional. NHS prescriptions are free or at standard prescription charge if eligible.
What happens if I'm not eligible for NHS tirzepatide?
If you don't meet NHS BMI or health criteria, private prescribing remains an option if you can afford it and pass a clinical assessment. Your GP can also signpost you to community weight management programmes (tier 1–2 services), which are free.
How long does it take to get tirzepatide on the NHS?
This varies significantly by region. Some ICBs have waiting lists of several months to over a year for tier 3 specialist services. Private access is typically faster — often within 1–2 weeks from consultation to first injection.
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.