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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Can You Take Mounjaro If You Have Diverticulitis?
If you have a history of diverticulitis and are considering Mounjaro for weight management, it's essential to discuss this with your GP before starting treatment. Mounjaro (tirzepatide) is a prescription-only weight loss injection that works as a dual GIP and GLP-1 receptor agonist. Diverticulitis — inflammation of small pouches in the colon — is a serious digestive condition that may affect how certain medications are tolerated. Your prescriber needs to assess your individual medical history to determine whether Mounjaro is appropriate and safe for you.
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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.
Medical Assessment and Diverticulitis Considerations
Mounjaro is not automatically contraindicated if you have diverticulitis, but it requires careful medical evaluation. One of Mounjaro's common side effects is gastrointestinal disturbance — including nausea, constipation, diarrhoea, and abdominal discomfort. For someone with a history of diverticulitis, these digestive effects need to be monitored closely. Additionally, Mounjaro slows gastric emptying (how quickly food moves through the stomach), which could theoretically complicate digestive function in people with inflammatory bowel conditions.
Your GP or prescriber will review your diverticulitis history — including frequency of flares, severity, and current management — before deciding if Mounjaro is suitable. They may recommend a lower starting dose, closer monitoring, or an alternative weight loss approach. This is why a clinical assessment with a qualified prescriber is non-negotiable; they need access to your full medical history, not just your weight and BMI.
You can use our free BMI calculator to check your current BMI, which helps inform the eligibility discussion with your prescriber. If you're eligible, they'll discuss your diverticulitis in detail before issuing a prescription.
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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 and Private Routes
In the UK, Mounjaro access depends on your route. Through the NHS, you'd be referred to a tier 3 specialist weight management service — however, NHS availability is very limited and varies significantly by region. Many areas have months-long waiting lists. Private prescription is often faster: you attend an online consultation with a UK-licensed prescriber, who reviews your medical history (including diverticulitis) and issues a prescription if appropriate. Private costs typically range from £129–£320 per month depending on dose, and treatment is dispensed by a GPhC-registered pharmacy.
Whether you access Mounjaro through the NHS or privately, the clinical assessment process is the same — your prescriber will discuss your diverticulitis thoroughly. Never start Mounjaro without mentioning your digestive history. Your GP can provide guidance on both routes and help you understand what to expect with dose titration and ongoing monitoring during treatment.
- 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 if I have diverticulitis?
Mounjaro is not automatically unsafe, but it requires individual medical assessment. Mounjaro causes gastrointestinal side effects (nausea, constipation, diarrhoea) and slows stomach emptying, which could affect someone with a history of diverticulitis. Your prescriber must review your specific diverticulitis history before deciding if it's appropriate. Always disclose your condition during clinical assessment.
What happens during the clinical assessment if I mention diverticulitis?
Your prescriber will ask detailed questions about your diverticulitis — when flares occur, severity, how often, and current management. They may recommend a lower starting dose, more frequent monitoring, or suggest an alternative approach. The assessment exists precisely to identify medical conditions that need special consideration before prescribing.
Can I take Mounjaro on the NHS if I have diverticulitis?
Yes, potentially — but you'd need referral to a specialist tier 3 weight management service through your GP. The service would assess your diverticulitis as part of the full clinical evaluation. NHS access is very limited and waiting lists are long in many areas. Your GP can discuss both NHS and private routes available to you.
What's the difference between Mounjaro and Wegovy for someone with diverticulitis?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) cause similar gastrointestinal side effects and require clinical assessment with a history of diverticulitis. Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is a GLP-1 agonist only. Your prescriber will advise which is more suitable based on your individual medical profile. Both require prescription and clinical assessment.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs range from approximately £129–£320 per month depending on dose (higher doses cost more). Prices vary between GPhC-registered online prescription services. You'll need an online consultation first — costs are only incurred after your prescriber approves treatment. Always confirm pricing before starting, as costs increase with dose escalation over the first 16–20 weeks.
Ready to take control of your weight loss journey?
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