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 With Diverticulitis?
If you have diverticulitis and are considering Mounjaro (tirzepatide) for weight management, you'll need specialist medical advice before starting treatment. Diverticulitis is an inflammatory bowel condition that affects how your digestive system works, and Mounjaro's mechanism—as a dual GIP and GLP-1 receptor agonist—directly impacts gut function. This guide explains the safety considerations and how to access appropriate medical assessment in the UK.
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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 Considerations and Digestive Health
Mounjaro works by slowing gastric emptying (how quickly food leaves your stomach) and affecting gut hormone pathways. For people with active or recent diverticulitis, this mechanism may not be suitable because:
- Slowed digestion can increase pressure in the colon, potentially triggering inflammation
- Changes to gut motility may complicate recovery from diverticular disease
- Nausea and constipation (common Mounjaro side effects) can worsen diverticulitis symptoms
- Individual assessment is essential—your medical history, severity of diverticulitis, and current health status all matter
Your GP or specialist prescriber must review your full medical history before any tirzepatide prescription. This is why Mounjaro is prescription-only and requires a clinical assessment. If you've had diverticulitis, mention this during your consultation. Alternatives like Wegovy (a GLP-1 agonist only, without the GIP component) or other weight management approaches may be discussed.
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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.
NHS vs Private Access Routes in the UK
NHS route: Referral to a tier 3 specialist weight management service through your GP. They will take your medical history (including any digestive conditions) and assess suitability. Regional availability varies significantly—some areas have longer waiting lists.
Private route: Online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. A clinical assessment is still required, and you'll be asked about medical conditions including bowel or digestive issues. Private prescriptions cost between £129–£320 monthly depending on dose. Either route requires a prescriber to confirm that Mounjaro is safe for your individual circumstances. Never start any weight loss medication without a professional clinical assessment, especially with a history of diverticulitis.
- 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 may not be suitable for people with active or recent diverticulitis because it slows gastric emptying and affects gut function, which could complicate your condition. You must discuss your medical history with a prescriber before any prescription. They'll assess whether Mounjaro or an alternative is appropriate for you.
What's the difference between Mounjaro and Wegovy for digestive conditions?
Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Both affect digestion, but they work via different pathways. Your prescriber may consider which mechanism is safer given your diverticulitis history. Neither is automatically ruled out, but individual assessment is crucial.
Can I get Mounjaro through the NHS if I have diverticulitis?
Yes, but you must be referred to a tier 3 specialist weight management service through your GP. The specialist team will review your full medical history, including your diverticulitis, and decide whether Mounjaro is safe or whether another approach is better suited.
What happens during an online consultation for Mounjaro?
A UK-licensed prescriber will ask about your medical history, current symptoms, medications, and any digestive or inflammatory conditions. You'll be asked specifically about bowel health. Based on this assessment, they'll either issue a prescription, suggest an alternative, or decline to prescribe if it's not safe for you.
How much does Mounjaro cost privately in the UK?
Private Mounjaro prescriptions typically cost £129–£320 per month depending on your dose (higher doses cost more). You'll need a UK prescription from a licensed prescriber following a clinical assessment. Costs don't include consultation fees, which vary by provider.
Ready to take control of your weight loss journey?
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