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 Medication for IBD in the UK
If you have inflammatory bowel disease (IBD) and are concerned about weight management, you may be eligible for prescription weight loss medication in the UK. Weight changes associated with IBD can happen due to malabsorption, medications like corticosteroids, or reduced activity during flare-ups. The good news is that several evidence-based treatment options are now available through the NHS and private prescribing. This guide explains your options, eligibility criteria, and how to start a conversation with your GP about whether prescription weight management might be right for you.
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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.
UK-Licensed Prescription Weight Loss Options
Three prescription weight loss medications are currently licensed in the UK for eligible adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonist medications (Mounjaro is a dual GIP/GLP-1 agonist) that work by regulating appetite and supporting feeling fuller after smaller meals.
In clinical trials, these medications helped participants achieve significant weight loss when combined with lifestyle changes. Mounjaro users lost an average of 15–21% of their body weight, whilst Wegovy users lost approximately 15% on average—though individual results vary considerably. All three require a prescription and clinical assessment before being prescribed.
- Mounjaro: once-weekly injection, doses 2.5–15 mg
- Wegovy: once-weekly injection, doses 0.25–2.4 mg
- Saxenda: once-daily injection, doses 0.6–3 mg
For adults with IBD specifically, weight loss medication may be particularly beneficial because it addresses appetite and satiety without requiring restrictive dieting, which can be difficult to manage alongside IBD symptoms.
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.
NHS Access vs Private Prescribing in the UK
In the UK, you can access prescription weight loss medication through the NHS or privately. NHS access is through specialist tier 3 weight management services—you'll need a referral from your GP and will be assessed based on BMI (usually 30 or above, or 27 with weight-related health conditions) and overall health. NHS availability varies significantly by region, and waiting lists can be lengthy in many areas.
Private prescribing is available through GPhC-registered online services following an online clinical assessment. This route doesn't require an NHS referral and is often faster, though there is a cost (typically £129–£320 monthly depending on dose). Your GP can advise whether you're eligible and which route suits your circumstances best. Use our free BMI calculator above to check your starting point, then speak with your GP about your options.
- 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 IBD?
Possibly, but it depends on your individual health and the type of IBD you have. GLP-1 medications can slow gastric emptying, which may affect symptom management in some people with IBD. You must discuss this directly with your GP or gastroenterologist before starting any weight loss medication to ensure it's safe for your specific condition and current treatments.
How do I know if I'm eligible for NHS weight loss medication?
You're typically eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions (such as type 2 diabetes or high blood pressure). For some ethnic groups, the threshold is lower. Your GP can assess your eligibility and refer you to a specialist weight management service if appropriate. Use our BMI calculator to check your current BMI as a starting point.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro users in trials lost slightly more weight on average (15–21%) compared to Wegovy users (approximately 15%), but individual results vary. Your prescriber will help determine which is more suitable for you.
Will weight loss medication work if I don't change my diet?
Prescription weight loss medications are most effective when combined with dietary changes and increased physical activity. They support appetite regulation and help you feel fuller, but they work best alongside lifestyle modifications. Your prescriber or a dietitian can help you make sustainable changes that work with your IBD.
How do I start the conversation with my GP about weight loss medication?
Simply ask your GP to discuss weight management options available to you. Mention your concerns about your weight and any weight-related health conditions you may have. Your GP can assess your eligibility, explain the medication options (NHS specialist services or private prescribing), discuss potential side effects, and help you decide on the best route forward for your situation.
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.