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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Weight Loss and Diverticulitis: UK Medication Guide
Managing weight when you have diverticulitis requires careful consideration, as both conditions affect digestive health. If you're looking to lose weight with this condition, prescription weight loss medication may be an option—but medical guidance is essential. This guide covers UK-licensed weight management options, eligibility criteria, and how to discuss your situation with your GP to find the safest approach for your health.
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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.
UK-Licensed Weight Management Medications for Adults with Diverticulitis
Three prescription weight loss medications are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, injected once weekly. Clinical trials showed average weight loss of 15–21% body weight over 72 weeks when combined with lifestyle changes.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, injected once weekly. Evidence demonstrates average weight loss of approximately 15% body weight at the maximum dose.
- Saxenda (liraglutide) — A GLP-1 receptor agonist, injected daily. May support modest weight loss alongside reduced-calorie diet and physical activity.
These medications work by reducing appetite and helping you feel fuller after smaller meals. However, diverticulitis affects digestive function, so your GP or specialist must assess whether any weight loss medication is safe for your specific situation before prescription.
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.
Eligibility and Next Steps: NHS vs Private Access
To be eligible for prescription weight loss treatment in the UK, you typically need a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Your GP can assess your eligibility and discuss whether weight management medication is appropriate given your diverticulitis history.
NHS access is through specialist tier 3 weight management services (usually via GP referral), though waiting times vary by region. Private options are available through UK-licensed prescribers following an online clinical assessment.
Start by speaking with your GP—they can refer you to specialist services, review your diverticulitis management, and determine the safest weight loss approach for you.
- 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.
Can I take weight loss injections if I have diverticulitis?
Weight loss medications like Mounjaro and Wegovy may affect digestive function, which is particularly relevant with diverticulitis. Your GP or gastroenterologist must assess your individual situation before any prescription. Never start weight loss medication without medical guidance if you have active or recurring diverticulitis.
What is the safest way to lose weight with diverticulitis?
Weight loss with diverticulitis should prioritise digestive health. A gradual approach (0.5–1 kg per week) is recommended. Dietary fibre intake, hydration, and avoiding trigger foods are often more important than gradual weight management. Your GP or dietitian can create a personalised plan that manages both conditions safely.
Does weight loss medication slow gastric emptying, and is that safe with diverticulitis?
Yes—GLP-1 medications slow how quickly food leaves the stomach, which can reduce appetite. However, this effect may interact with diverticulitis management. Discuss this specifically with your GP or specialist before starting any weight loss medication to ensure it won't compromise your digestive health.
Should I use the BMI calculator if I have diverticulitis?
Yes, our free BMI calculator helps you understand your weight in health context. However, BMI is just one measurement. Your GP should assess your overall health, including diverticulitis management, before recommending any weight loss approach—medication or otherwise.
How do I get weight loss medication on the NHS with diverticulitis?
Ask your GP for a referral to a specialist weight management service (tier 3). Be clear about your diverticulitis history in your assessment. The specialist team will determine if prescription weight loss medication is safe for you and manage the interaction with your existing digestive condition.
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.