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
Gastroparesis and Mounjaro: UK Access and Cost Guide
Gastroparesis is a condition where the stomach empties more slowly than normal. If you have gastroparesis, Mounjaro may not be suitable — the medication slows gastric emptying further. This guide explains how to access tirzepatide in the UK, the true costs involved, NHS eligibility criteria, and what the online prescription process looks like. Whether you're exploring weight management options or concerned about medication compatibility with existing health conditions, understanding the practical access routes and cost implications is essential.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
UK Private Cost and NHS Access Routes
Mounjaro (tirzepatide) is available through two main routes in the UK: NHS specialist services and private prescription. NHS access is available through tier 3 specialist weight management services, but requires GP referral and eligibility assessment. Many NHS areas have significant waiting lists — often several months to over a year depending on your region. Private prescription costs typically range from £129 to £320 per month depending on dose, with most users starting at 2.5 mg (approximately £129–£160) and progressing to higher doses. Each KwikPen contains 4 weeks of treatment. Private prescriptions require an online consultation with a UK-licensed prescriber, which usually costs £15–£50 separately. Our GLP-1 weight loss calculator can help you estimate potential costs and outcomes at different doses.
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 Prescription Process and Eligibility Considerations
To access Mounjaro privately in the UK, you complete an online health questionnaire assessed by a UK-licensed prescriber. If approved, a prescription is issued and dispensed by a registered GPhC pharmacy. The entire process typically takes 24–48 hours. Important: gastroparesis is a contraindication — the prescriber will ask about existing stomach conditions during assessment. Eligibility requires a BMI of 30 or above, or 27+ with weight-related health conditions like type 2 diabetes, hypertension, or cardiovascular disease. Use our free BMI calculator above to check whether you fall within eligibility thresholds. Those taking oral medications should note that Mounjaro may reduce absorption, requiring timing adjustments.
- 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 get Mounjaro on the NHS if I have gastroparesis?
No. Gastroparesis is a contraindication for Mounjaro because the medication slows stomach emptying, which would worsen symptoms. Your GP or specialist can discuss alternative weight management options suitable for your condition.
How much does Mounjaro cost privately in the UK per month?
Private costs range from approximately £129–£320 per month depending on your dose. Starting dose (2.5 mg) costs around £129–£160 monthly. Higher doses (10–15 mg) may cost £250–£320. Prescription fees are usually £15–£50 additional.
What's the difference between NHS and private Mounjaro access in the UK?
NHS access requires GP referral to specialist weight management services with often lengthy waiting lists. Private access is faster (24–48 hours) via online prescription but costs more. NHS availability varies significantly by region; private is available nationwide through GPhC-registered pharmacies.
How long does the private online prescription process take for Mounjaro?
Most online consultations are assessed within 24 hours. If approved, your prescription is issued and dispensed the same day or next working day. You should receive your KwikPen within 2–5 working days depending on the pharmacy's delivery service.
Will Mounjaro affect my other medications if I get it privately?
Yes. Mounjaro may reduce absorption of oral medications, particularly oral contraceptives. The prescriber will ask about all medications during assessment. Those on oral contraceptives should use barrier methods for 4 weeks after starting and after each dose increase.
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.