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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Taking Mounjaro After Gallbladder Removal
If you've had your gallbladder removed, you may wonder whether Mounjaro (tirzepatide) is safe for you. The short answer is that people without a gallbladder can potentially take Mounjaro, but this requires careful assessment by your prescriber. Since your gallbladder stores bile to help digest fats, its absence can affect how your digestive system works — and this matters when considering any medication that affects digestion. Your GP or prescribing healthcare professional will need to evaluate your individual situation before any prescription is issued.
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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 is a dual GIP and GLP-1 receptor agonist — it works by activating two natural hormone pathways that regulate appetite and blood sugar. Part of how it works is by slowing gastric emptying (how quickly food moves from your stomach into your intestines). This effect typically reduces over time as your body adjusts.
Without a gallbladder, your body produces bile continuously rather than storing it for use during meals. This changes how you digest fats and fatty foods. When combined with a medication that slows digestion, some people experience increased gastrointestinal side effects like nausea, diarrhoea, or indigestion. Mounjaro's common side effects already include stomach discomfort — and this may be more pronounced if you don't have a gallbladder.
This doesn't automatically mean you cannot take Mounjaro, but your prescriber needs to know about your gallbladder removal so they can assess the risk versus benefit for your specific health situation.
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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 You Must Tell Your Prescriber
Before starting Mounjaro — whether through NHS specialist services or private prescription — you must tell your prescriber that you've had your gallbladder removed. Include the date of your surgery and whether you experienced any ongoing digestive issues afterwards, such as chronic diarrhoea or fatty food intolerance.
Your prescriber will use this information to decide whether Mounjaro is appropriate for you, whether a different weight loss medication might be safer (such as Wegovy, which is a single GLP-1 agonist rather than dual mechanism), or whether additional monitoring is needed. If you have a history of pancreatitis or bile duct problems, this is also critical to disclose — Mounjaro carries a small risk of pancreatitis, and your medical history affects this assessment.
Never start Mounjaro without clinical assessment, and never withhold information about previous surgery from your healthcare team.
- 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 Mounjaro if I don't have a gallbladder?
Potentially yes, but only after clinical assessment. Your prescriber must know about your gallbladder removal before issuing a prescription. Since Mounjaro affects digestion and your body handles digestion differently without a gallbladder, this requires individual evaluation. Your GP or licensed prescriber will weigh the benefits against potential risks for your situation.
Will side effects be worse without a gallbladder?
You may experience more digestive side effects like nausea, diarrhoea, or indigestion because Mounjaro slows stomach emptying and your body already manages bile differently. However, not everyone without a gallbladder has worse side effects — it varies significantly. Your prescriber can discuss what to expect based on your individual health history.
What should I tell my prescriber about my gallbladder removal?
Tell them the date of surgery, any ongoing digestive symptoms (like chronic diarrhoea or fatty food intolerance), any history of pancreatitis, and how your digestion has been managed since removal. This information helps them decide if Mounjaro is safe for you or if an alternative weight loss medication might be better.
Is there an alternative to Mounjaro if I don't have a gallbladder?
Yes. Wegovy (semaglutide) is a single GLP-1 agonist that may cause fewer digestive complications than Mounjaro's dual mechanism, though it still affects gastric emptying. Saxenda (liraglutide) is another option. Your prescriber can discuss which licensed weight loss medication is most appropriate for your individual situation.
Where do I get assessed for Mounjaro if I've had surgery?
NHS access is through specialist tier 3 weight management services (referral from your GP). Private access is through UK-licensed prescribers using online consultations. In both cases, you'll complete a health questionnaire that asks about previous surgery — this is your opportunity to disclose gallbladder removal so your prescriber can make a proper assessment.
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