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
Can Mounjaro Cause Cancer?
There is no evidence that Mounjaro (tirzepatide) causes cancer in people, based on current clinical trial data and MHRA safety monitoring. However, any prescription weight loss medication carries risks that your GP should discuss with you before starting treatment. This guide explains what NHS guidance and clinical evidence show about Mounjaro safety, how it compares to other weight loss treatments like Wegovy, and what you need to know before your clinical assessment.
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.
What the Clinical Evidence Shows
Mounjaro was approved by the MHRA (Medicines and Healthcare products Regulatory Authority) following rigorous safety testing in the SURMOUNT clinical trials. These trials monitored thousands of participants over 72 weeks and did not identify cancer as a side effect. The most common side effects reported were gastrointestinal — nausea, diarrhoea, vomiting, and constipation — rather than cancer-related concerns.
Mounjaro carries MHRA additional monitoring status (indicated by a Black Triangle ▼), which means it is monitored continuously for new safety signals. If any cancer link emerged during post-market use, the MHRA would investigate and communicate this to healthcare professionals immediately. To date, no such signal has been identified.
It is important to understand that weight loss itself reduces cancer risk. Excess weight is linked to increased risk of 13 cancer types, including breast, bowel, and endometrial cancer. For many people, the health benefits of weight loss through Mounjaro may outweigh the risks — but this is an individual decision to discuss with your GP or prescriber.
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.
Mounjaro Safety Compared to Other Weight Loss Treatments
Mounjaro is a dual GIP and GLP-1 receptor agonist, which differs from Wegovy (semaglutide), a GLP-1-only medication. Both are prescription-only and both have undergone formal safety assessment. Neither has shown a link to cancer in clinical trials.
The dose titration schedule for Mounjaro — starting at 2.5 mg and gradually increasing to a maximum of 15 mg — allows your prescriber to monitor your individual response and side effects carefully. All serious side effects must be reported to your GP immediately, including any unusual symptoms or health changes.
Your eligibility for Mounjaro through NHS specialist tier 3 weight management services, or via private prescription after clinical assessment, depends on your BMI and weight-related health conditions. Use our free GLP-1 weight loss calculator to understand potential outcomes, and our BMI calculator to check where you fall on NHS eligibility thresholds.
- 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.
Has anyone gotten cancer from Mounjaro?
No cases of cancer directly caused by Mounjaro have been reported in clinical trials or post-market safety data. The SURMOUNT trials (the main safety studies) involved thousands of participants and found no increased cancer risk. Mounjaro is under continuous MHRA monitoring, so any new safety signal would be detected and communicated to healthcare professionals.
Is Mounjaro safe to use long-term?
The longest clinical trials lasted 72 weeks, so long-term safety beyond this period is still being studied. The MHRA's Black Triangle status means Mounjaro is actively monitored for emerging safety concerns. Your GP or prescriber will assess whether continuing treatment is appropriate for you based on your individual health and response.
What are the actual side effects of Mounjaro?
The most common side effects are gastrointestinal: nausea, diarrhoea, vomiting, constipation, and stomach pain. These often improve as your body adjusts. Serious but rare side effects include pancreatitis (severe stomach pain), gallbladder issues, and severe allergic reactions. Report any concerning symptoms to your GP immediately.
Should I be worried about cancer risk with Mounjaro vs Wegovy?
Both Mounjaro and Wegovy have undergone rigorous safety testing and show no increased cancer risk in clinical trials. The choice between them depends on your individual health profile, prescriber recommendation, and how your body responds. Your GP or licensed prescriber will assess which is appropriate for you during your clinical assessment.
Does losing weight with Mounjaro reduce my cancer risk?
Yes. Excess weight is linked to 13 cancer types. Losing 5–10% of body weight can meaningfully reduce cancer risk and improve other health markers like blood pressure and blood sugar control. For many people, the cancer risk reduction from weight loss outweighs medication risks — but discuss this with your GP.
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.