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 After Gallbladder Surgery: Managing Your Health
Many people experience weight changes following gallbladder removal (cholecystectomy). Some gain weight due to metabolic changes and altered fat digestion, while others lose weight initially. If you're struggling with excess weight management after surgery, UK prescription options are available. Understanding your BMI and exploring evidence-based weight management strategies—including lifestyle changes and, if eligible, prescription medication—can help you achieve a healthier weight. Our free BMI calculator can help you assess your current health status and determine what healthy weight looks like for your height.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Prescription Weight Management Options
If you've gained weight after gallbladder surgery and have a BMI of 30 or above (or 27 or above with weight-related health conditions), you may be eligible for prescription weight loss medication available in the UK.
Three main options are licensed:
- Mounjaro (tirzepatide) — a dual GIP/GLP-1 injection (2.5–15 mg weekly) that may help reduce appetite and support feeling fuller after meals
- Wegovy (semaglutide) — a GLP-1 injection (0.25–2.4 mg weekly) approved for weight management in eligible adults
- Saxenda (liraglutide) — a daily GLP-1 injection option
In clinical trials, these medications helped people lose an average of 15–21% of body weight alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly, and eligibility is assessed on an individual basis by a prescriber. Our GLP-1 weight loss calculator can help you understand potential weight loss at different doses.
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 vs Private Access in the UK
NHS access: Available through specialist tier 3 or 4 weight management services by GP referral. Availability and waiting times vary significantly across regions. Many areas have extended waiting lists.
Private access: Available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This often provides faster access without NHS referral. Your GP can discuss which route is most appropriate for your circumstances, especially given your post-surgery status.
To find out if you're eligible, use our free BMI calculator above to check your current BMI, then speak with your GP or a licensed prescriber about your individual situation.
- 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 after gallbladder surgery?
Yes, if you meet eligibility criteria (BMI 30+ or 27+ with health conditions). However, inform your prescriber about your surgery. Some people post-cholecystectomy experience fat malabsorption, which may affect how medications work or absorption of oral medicines. A prescriber will assess whether GLP-1 medication is suitable for your individual health profile.
Why do some people gain weight after gallbladder removal?
After cholecystectomy, bile flows continuously rather than being released during meals, which can affect fat digestion and metabolism. Some people experience increased appetite, metabolic changes, or altered eating patterns. Weight gain is common but manageable through diet, exercise, and—if eligible—prescription medication and weight management UK strategies.
How quickly can I expect weight loss with these medications?
Clinical trials showed average weight loss of 15–21% of body weight over several months to a year, though individual results vary significantly. Weight loss typically becomes noticeable after 4–8 weeks at therapeutic doses. Results depend on your starting weight, the dose, adherence, and lifestyle changes including reduced-calorie diet and increased physical activity.
Will my GP prescribe Mounjaro or Wegovy on the NHS?
Your GP can refer you to a specialist weight management service (tier 3), but prescribing happens through those specialist services, not standard GP practice. Availability varies by region and waiting times can be lengthy. Private prescribing through an online assessment is often faster if you prefer not to wait.
Is there anything special I should tell a prescriber about my gallbladder surgery?
Yes—mention your cholecystectomy when discussing weight loss medication. Your prescriber needs to know because post-surgery fat malabsorption may interact with GLP-1 medications or affect oral medication absorption. This information helps them assess suitability and recommend the right treatment approach for your specific circumstances.
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.