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
Side Effects of Mounjaro: Cost and Access in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. Before considering this medication, it's important to understand both the common side effects and the practical costs and access routes available. Whether you're eligible for NHS access or considering private prescription, this guide explains what to expect and how much Mounjaro typically costs in the UK. Use our free BMI calculator above to check your eligibility first, or our GLP-1 weight loss calculator to estimate potential outcomes.
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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.
Common Side Effects and What They Mean for Cost Decisions
Mounjaro's most common side effects are gastrointestinal — nausea, diarrhoea, vomiting, constipation, and stomach pain affect more than 1 in 10 people, especially when starting or increasing doses. These typically improve over time as your body adjusts. Other frequent effects include indigestion, fatigue, dizziness, injection site reactions, and hair loss. Understanding these side effects is important because they may influence your decision about whether this medication suits your lifestyle and budget. Many people find side effects manageable and temporary, but some experience persistent symptoms. This matters when weighing the cost against expected benefits. The dual GIP and GLP-1 mechanism of tirzepatide (Mounjaro's active ingredient) means it may have a stronger effect on appetite and digestion compared to single-action GLP-1 medications like Wegovy, which can result in more pronounced initial side effects but often greater weight loss.
- Nausea and vomiting usually ease within 2–4 weeks
- Diarrhoea or constipation may require dietary adjustment
- Injection site reactions are typically mild and brief
- Serious side effects (pancreatitis, gallbladder issues) are rare but require immediate medical attention
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 Cost and How to Access Mounjaro
Private prescription cost: Mounjaro typically costs £129–£320 per month in the UK through private online prescribing, depending on your dose. The starting dose (2.5 mg) is cheaper than the maximum dose (15 mg). A full four-week supply (one KwikPen) is usually one month's cost. NHS access: Mounjaro is available through NHS specialist weight management services (tier 3), but access is limited and varies significantly by region. Waiting lists can be months to years long. Your GP must refer you to your local specialist service, and eligibility is assessed individually. Many people find private prescription faster if they meet the clinical criteria. Whether you choose NHS or private, always discuss side effect management with your prescriber beforehand. Track your progress using our free progress tracker once you start.
- 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.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose. Starting doses are cheaper than maintenance doses. A standard four-week supply (one KwikPen with four weekly injections) represents one month's cost. Prices vary between providers, so compare before committing.
Can I get Mounjaro free on the NHS?
Yes, Mounjaro is available through NHS specialist weight management services for eligible adults. However, access is limited and varies by region. You'll need a GP referral to your local tier 3 weight management service. Waiting lists are often long (months to years in many areas), so many people choose private prescription instead.
What is the safest dose for side effect management?
The starting dose of 2.5 mg is designed to minimise side effects. Your prescriber will typically increase the dose every 4 weeks if tolerated. Most side effects settle within 2–4 weeks as your body adjusts. Never skip doses or increase faster than prescribed — always follow your prescriber's guidance.
Is Mounjaro worth the cost if side effects are bad?
This depends on individual tolerance. Some people find side effects manageable and temporary; others experience persistent issues. Discuss this with your prescriber before starting. If you do start and find side effects unbearable, your prescriber can reduce your dose, pause treatment, or switch you to an alternative like Wegovy, which has a gentler dose escalation.
How do I get a private Mounjaro prescription in the UK?
Private prescriptions require an online consultation with a UK-licensed prescriber. You'll answer health questions, receive a clinical assessment, and if eligible, get a prescription. This is dispensed by a GPhC-registered pharmacy. The whole process typically takes 1–3 working days, much faster than NHS waiting lists.
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.