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
Mounjaro Side Effects, Cancer Risk, and How to Access in the UK
Mounjaro (tirzepatide) is a prescription-only GLP-1 medication licensed in the UK for weight management. Questions about potential side effects, including cancer risk, are common and important. This guide explains what clinical evidence shows about safety, clarifies cancer concerns based on current research, and outlines your options for accessing Mounjaro in the UK — both through the NHS and privately. Individual eligibility and costs vary significantly depending on your route of access and which GLP-1 weight loss calculator projections match your situation.
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.
Mounjaro Side Effects and Cancer Safety Concerns
Clinical trials for Mounjaro (tirzepatide) have not identified cancer as a direct side effect. However, like all medications, Mounjaro carries potential side effects that you should understand. The most common side effects are nausea, diarrhoea, vomiting, and constipation — particularly during dose titration when your body is adjusting to each new strength.
- Very common side effects (affecting more than 1 in 10 users): nausea, diarrhoea, vomiting, constipation, stomach pain
- Common side effects: indigestion, headache, fatigue, dizziness, injection site reactions, hair loss
- Serious but rare: pancreatitis (severe stomach pain), gallbladder problems, serious allergic reactions
Regarding cancer specifically: the MHRA (UK medicines regulator) continues to monitor tirzepatide safety. Some GLP-1 medications have shown increased medullary thyroid cancer risk in animal studies, but this has not been confirmed in human trials. The MHRA advises that individuals with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia (MEN2) should not take GLP-1 medications. Your prescriber will assess your individual risk during clinical assessment.
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.
Accessing Mounjaro in the UK: NHS vs Private Routes and Costs
NHS Access: Mounjaro is available through NHS specialist tier 3/4 weight management services following NICE guidance. You must be referred by your GP to a specialist weight management centre. Availability and waiting times vary significantly by region — some areas have waiting lists of 6–12+ months. Once prescribed, Mounjaro is supplied free on the NHS if you meet eligibility criteria.
Private Access: You can obtain a prescription privately through UK-licensed online prescribing services. The process involves a clinical consultation (online questionnaire and/or video call with a registered prescriber), assessment of your eligibility, and if suitable, prescription issue to a GPhC-registered pharmacy. Private costs range from approximately £129–£320 per month depending on your dose, with treatment starting at the lowest dose (2.5 mg) and titrating upwards over weeks. Use our GLP-1 weight loss calculator to estimate potential results at different doses.
Private Prescription Timeline: Most private consultations are completed within 24–48 hours. Your first prescription is typically available within 2–5 working days. Subsequent monthly doses are usually dispatched within 48 hours of placing a repeat order.
What to Expect During Assessment: A licensed prescriber will ask about your medical history, current medications, BMI (use our free BMI calculator to check yours), weight-related health conditions, and any contraindications. You'll need to disclose any family history of thyroid cancer, pancreatitis risk, gallbladder disease, or pregnancy plans. The prescriber determines whether Mounjaro or an alternative like Wegovy is more suitable for you based on individual factors. You should also use the weight converter to ensure you understand your current weight in both kg and stone.
- 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.
Is Mounjaro safe regarding cancer risk?
Clinical trials have not identified cancer as a side effect of tirzepatide (Mounjaro). The MHRA continues to monitor safety. However, individuals with a personal or family history of medullary thyroid cancer or MEN2 syndrome should not take Mounjaro. Your prescriber will assess your individual risk during clinical consultation.
How much does Mounjaro cost privately in the UK?
Private costs typically range from £129–£320 per month depending on your dose. The starting dose (2.5 mg) is usually the most affordable, with costs increasing at higher maintenance doses. Prices vary between different GPhC-registered online prescribing services, so it's worth comparing.
Can I get Mounjaro free on the NHS?
Yes, Mounjaro is available free on the NHS through specialist tier 3/4 weight management services. You need a referral from your GP. Eligibility and waiting times vary by region — some areas have significant waiting lists. Availability depends on your local integrated care board (ICB) commissioning.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are licensed for UK weight management, but Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, while Wegovy (semaglutide) is GLP-1-only. Mounjaro may have a slightly stronger effect, but individual results vary. Your prescriber will determine which is more suitable based on your health profile and eligibility.
What happens during the online consultation for private Mounjaro?
A UK-licensed prescriber reviews your health questionnaire or conducts a video consultation, assesses your BMI and weight-related conditions, checks for contraindications (especially thyroid or pancreatic history), reviews current medications, and determines if you're eligible. If suitable, a prescription is issued to a GPhC pharmacy. The entire process typically takes 24–48 hours.
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.