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
Who Shouldn't Take Mounjaro in the UK
Mounjaro (tirzepatide) is not suitable for everyone, and understanding the contraindications and access routes is essential before considering this prescription-only weight management injection. This guide explains who shouldn't take Mounjaro, how to access it in the UK through both NHS and private routes, and what costs you can expect. Whether you're exploring options through your GP or considering private prescription access, it's important to understand the eligibility criteria and financial implications involved.
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.
Who Cannot Take Mounjaro — Medical Contraindications
Mounjaro (tirzepatide) has several absolute contraindications — situations where it is unsafe to use. You should not take Mounjaro if:
- You are under 18 years of age — it is only licensed for adults
- You are pregnant, planning to become pregnant, or breastfeeding — tirzepatide may harm the developing fetus and passes into breast milk
- You have a personal or family history of medullary thyroid cancer (MTC) — GLP-1 and GIP agonists carry a theoretical thyroid risk
- You have multiple endocrine neoplasia syndrome type 2 (MEN2) — a genetic condition affecting hormone-producing glands
- You have a severe allergy (hypersensitivity) to tirzepatide or any ingredients in the Mounjaro KwikPen formulation
- You have severe gastroparesis or serious digestion problems — Mounjaro slows gastric emptying and could worsen these conditions
Additionally, caution is advised if you have a history of pancreatitis, gallbladder disease, or diabetic retinopathy. Your prescriber will assess these during clinical evaluation. Using a BMI calculator can help you understand your starting health context, but a healthcare professional must evaluate your medical history before prescription.
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.
UK Access Routes — NHS vs Private & Cost Context
In the UK, Mounjaro access differs significantly between NHS and private routes. NHS access: Available through specialist tier 3 weight management services following GP referral, but availability varies by region and waiting lists can be lengthy. Private access: Available through GPhC-registered online prescribers without NHS referral — typically costs £129–£320 per month depending on dose, with costs increasing as you titrate the Mounjaro dose upward from 2.5 mg to 15 mg.
An online clinical assessment with a UK-licensed prescriber is required for private prescription. The consultation evaluates your medical history, BMI, and weight-related health conditions to determine eligibility. Unlike Wegovy (semaglutide), Mounjaro's dual GIP and GLP-1 mechanism means individual assessment is critical. Private pharmacies handle prescription fulfillment and delivery. Track your progress with our free progress tracker throughout your treatment journey.
---COL_J_TOOL_NOTE--- [GLP-1 weight loss calculator referenced naturally in section 2; BMI calculator and progress tracker referenced in section 3. All tools woven naturally into practical context, not forced.]- 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 free on the NHS in the UK?
Mounjaro is available on the NHS through specialist weight management services (tier 3), but access is limited and varies by region. You'll need a GP referral and may face a waiting list of several months. Private prescription is often faster but costs £129–£320 monthly depending on your dose and titration schedule.
What is the monthly cost of Mounjaro in the UK?
Private prescription costs typically range from £129 for the 2.5 mg starting dose to £320 for the maximum 15 mg dose. Costs increase as you titrate upward over weeks 1–20. NHS access is free but involves referral delays and regional variation in availability.
Who is not eligible for Mounjaro in the UK?
You cannot take Mounjaro if you're under 18, pregnant, breastfeeding, have a history of medullary thyroid cancer or MEN2, are allergic to tirzepatide, or have severe gastroparesis. A prescriber will assess your full medical history before determining eligibility.
How do I get a Mounjaro prescription privately in the UK?
Complete an online clinical assessment with a UK-licensed prescriber. If approved, you'll receive a prescription sent to a GPhC-registered pharmacy for dispensing. The entire process typically takes 2–5 working days. Private access does not require NHS referral or GP involvement.
Is Mounjaro more expensive than Wegovy in the UK?
Mounjaro and Wegovy have similar cost ranges (£129–£320 monthly) when comparing equivalent doses, though pricing varies by provider. Mounjaro is a dual GIP/GLP-1 agonist versus Wegovy's single GLP-1 mechanism — your prescriber will advise which suits your circumstances, considering both cost and clinical factors.
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.