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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Mounjaro Risks — Understanding UK Cost and Access
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK through both NHS specialist services and private prescribing routes. While clinical trials have demonstrated weight loss results, understanding the associated risks, costs, and access options is essential before considering treatment. This guide explains how to access Mounjaro in the UK, what it costs, and what health risks you should be aware of alongside eligibility criteria. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses.
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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.
UK Access Routes and Costs for Mounjaro
Mounjaro is available in the UK through two distinct routes: NHS specialist services and private prescribing. NHS access is through tier 3 or 4 specialist weight management services, typically following referral from your GP. NICE has approved tirzepatide for NHS use, but availability varies significantly by region, and waiting lists can be lengthy. Private prescribing offers faster access through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber — usually available within days rather than months.
Private Mounjaro costs typically range from £130 to £350 per month depending on the dose you're prescribed. The KwikPen device contains four weekly doses, so costs represent a month's supply. Your prescriber will start you on the lowest dose (2.5 mg) and escalate gradually based on tolerance and response, with the maximum dose being 15 mg once weekly. Neither NHS nor private treatment is assured to produce weight loss — individual results vary, and tirzepatide works best alongside reduced-calorie diet and increased physical activity. Use our BMI calculator to establish your starting point before beginning any weight management programme.
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.
Health Risks and NHS vs Private Considerations
Key health risks with Mounjaro include gastrointestinal side effects (nausea, vomiting, diarrhoea are very common), potential pancreatitis (seek urgent care if severe stomach pain develops), and gallbladder problems. Mounjaro may affect absorption of oral contraceptives and other oral medications. Those with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 should not use tirzepatide.
NHS route advantages: Fully funded, includes NHS monitoring, and prescriber oversight. Disadvantages: Long waits, regional variation, may be deprioritised. Private route advantages: Fast access, choice of prescriber, flexible scheduling. Disadvantages: Out-of-pocket cost, personal responsibility for monitoring. Whichever route you choose, a qualified prescriber must assess your eligibility based on BMI (typically 30+ or 27+ with health conditions) and overall health status. Your GP can advise which route suits your circumstances.
- 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 does Mounjaro cost on the NHS?
Mounjaro is free on the NHS if prescribed through specialist tier 3 or 4 weight management services. However, access varies significantly by region and waiting times can be several months. Your GP can refer you, but eligibility and availability depend on your local integrated care board (ICB) commissioning decisions.
How much does private Mounjaro cost in the UK?
Private Mounjaro typically costs £130–£350 per month depending on dose. Each KwikPen contains four weekly doses (one month's supply). Starting dose is 2.5 mg, escalating to 15 mg maximum. Costs are paid out-of-pocket and are not covered by standard health insurance in the UK.
What are the main health risks associated with Mounjaro?
Common side effects include nausea, vomiting, diarrhoea, and constipation. Serious risks include pancreatitis (severe stomach pain), gallbladder problems, and potential complications in those with thyroid cancer history. Most side effects improve over time, but persistent symptoms should be reported to your prescriber immediately.
How long does it take to get Mounjaro on the NHS versus privately?
NHS access typically takes 3–12 months from GP referral to first prescription, depending on local waiting lists. Private prescribing is usually faster — many patients receive their first prescription within 1–7 days of online consultation following clinical assessment.
Can I switch between NHS and private Mounjaro?
Yes, you can switch between NHS and private routes. However, any change in prescriber should involve discussion about your current dose and response. If switching from private to NHS, inform your new NHS prescriber of your current dose and any side effects you've experienced to ensure continuity of care.
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.