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 You Take Mounjaro With Diverticulitis?
If you have diverticulitis or a history of inflammatory bowel conditions and are considering Mounjaro (tirzepatide), it's crucial to discuss this with your GP before starting treatment. Mounjaro works by slowing gastric emptying and affecting digestive function, which may interact with diverticulitis. This guide explains what you need to know about Mounjaro safety with diverticulitis and how to have the right conversation with your healthcare team about eligibility and risk.
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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.
How Mounjaro Affects Digestion
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that works partly by slowing how quickly food moves through your stomach and intestines — a process called gastric emptying. This mechanism helps create feelings of fullness and supports weight loss, but it also means Mounjaro directly affects your digestive system.
Diverticulitis is inflammation of small pouches (diverticula) in the colon. When taking any medication that alters digestive function, there is potential for interaction or complications. Common Mounjaro side effects include nausea, constipation, diarrhoea, and abdominal pain — symptoms that can overlap with or complicate existing diverticulitis symptoms, making it harder to distinguish between medication effects and disease flare-ups.
Additionally, constipation caused by Mounjaro could theoretically increase diverticulitis risk in susceptible individuals, as reduced bowel movement and increased intestinal pressure are contributing factors to diverticulitis episodes.
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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.
What Your GP Needs to Know
Before starting Mounjaro, you must inform your prescriber of any history of diverticulitis, inflammatory bowel disease, or severe gastrointestinal conditions. Your GP or specialist will weigh your weight management needs against the digestive risks specific to your medical history.
In many cases, Mounjaro may still be prescribed with careful monitoring, but your healthcare team needs to make this assessment individually. You may be advised to start at the lowest dose (2.5 mg) with close follow-up, or alternative weight loss options may be recommended. Never start Mounjaro without medical clearance if you have active or recent diverticulitis — the medication may worsen symptoms or complicate treatment.
Use our free GLP-1 weight loss calculator to understand how Mounjaro works, then discuss findings with your GP before any prescription is issued.
- 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 had diverticulitis in the past?
Possibly, but only your GP can decide. A history of diverticulitis does not automatically exclude you from Mounjaro, but your prescriber must assess your individual risk. Be fully transparent about frequency, severity, and timing of past episodes. Your doctor may recommend closer monitoring or suggest alternatives.
Can Mounjaro cause diverticulitis?
Mounjaro does not directly cause diverticulitis, but by slowing digestion and sometimes causing constipation, it may increase risk in people already susceptible to the condition. This is why medical clearance is essential before starting treatment.
What should I do if I develop abdominal pain while taking Mounjaro?
Contact your GP immediately. Severe, persistent stomach pain — especially pain spreading to the back — requires urgent assessment. It could indicate diverticulitis, pancreatitis, or another serious condition. Do not assume it is a normal Mounjaro side effect without medical evaluation.
Are there weight loss alternatives if I cannot take Mounjaro?
Yes. Your GP may suggest Wegovy (semaglutide, a GLP-1 agonist only — not dual mechanism like Mounjaro), lifestyle changes, dietary support, or other approaches. Discuss all options with your healthcare team based on your digestion history and overall health needs.
Does the NHS prescribe Mounjaro to people with diverticulitis?
The NHS assesses each patient individually through specialist weight management services. Diverticulitis does not automatically disqualify you, but you must declare it. NHS availability also varies significantly by region and specialist service capacity in your area.
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.