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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Pain Under Ribs on Mounjaro: What You Need to Know
Pain under the ribs whilst taking Mounjaro (tirzepatide) can be concerning, but understanding what's causing it is the first step. This pain may relate to how Mounjaro works in your body, or it could be unrelated to the medication itself. This guide explains the possible causes, when to contact your GP, and how to manage this symptom safely within NHS guidelines.
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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.
Possible Causes of Rib Pain While Taking Mounjaro
Mounjaro is a dual GIP and GLP-1 receptor agonist that affects how your digestive system works. Pain under the ribs can stem from several causes:
- Gastric changes: Mounjaro slows how quickly food leaves your stomach (gastric emptying), which can cause discomfort, bloating, and referred pain under the ribs or across your upper abdomen
- Gallbladder issues: gradual weight management or changes in fat metabolism may increase gallstone risk — gallbladder pain often radiates under the right rib cage
- Pancreatitis: Severe, persistent upper abdominal or rib pain spreading to the back is a medical emergency and may indicate pancreatitis — seek immediate medical attention
- Muscle strain: Nausea and vomiting caused by Mounjaro can strain abdominal muscles, causing rib pain
- Unrelated causes: The pain may not be related to Mounjaro at all — other conditions like musculoskeletal pain, acid reflux, or rib inflammation can occur independently
Because Mounjaro affects your digestive system significantly, it's essential to distinguish between expected side effects and symptoms that require urgent medical evaluation.
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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.
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When to Contact Your GP About Rib Pain
Contact your GP if you experience:
- Persistent pain under the ribs lasting more than a few days
- Pain that worsens despite resting or taking over-the-counter pain relief
- Pain accompanied by yellowing of skin or eyes (jaundice)
- Fever or chills alongside rib pain
- Difficulty breathing or chest tightness
- Severe bloating or inability to keep food down
Seek emergency medical attention (call 999 or go to A&E) if you experience: Severe, sudden pain under the ribs spreading to your back, severe vomiting, or signs of pancreatitis. Do not wait for a routine appointment — these may indicate a serious condition requiring urgent evaluation. Always inform your prescriber or GP that you're taking Mounjaro, as this affects how they assess your symptoms.
- 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 rib pain a common side effect of Mounjaro?
Rib pain is not listed as a common side effect in clinical trials, but gastrointestinal discomfort (nausea, stomach pain, bloating) is very common. Pain under the ribs may result from these digestive changes or be unrelated to Mounjaro. Always report new or unusual pain to your GP.
Should I stop taking Mounjaro if I have rib pain?
Do not stop taking Mounjaro without consulting your prescriber or GP first. If the pain is mild and clearly related to stomach discomfort, it may settle as your body adjusts. However, if pain is severe, persistent, or accompanied by other symptoms, contact your healthcare provider immediately for guidance.
Could rib pain be a sign of gallstones from Mounjaro?
gradual weight management can increase gallstone risk in some people. Gallbladder pain typically appears under the right rib cage and may come and go. If you suspect gallbladder issues, your GP can arrange an ultrasound scan. Report any new pain patterns to your prescriber promptly.
What's the difference between pancreatitis pain and normal Mounjaro side effects?
Pancreatitis causes severe, constant pain in the upper abdomen or under the ribs, often radiating to the back. It's accompanied by severe nausea or vomiting and may cause fever. This is a medical emergency. Regular Mounjaro side effects (mild bloating or stomach discomfort) are usually manageable and improve over time.
How can I manage rib pain whilst waiting to see my GP?
If pain is mild, try resting, eating smaller meals, staying hydrated, and avoiding fatty foods (which slow digestion further). Over-the-counter paracetamol or ibuprofen may help, but do not delay seeking medical advice if pain persists. Use our free progress tracker to log when pain occurs and any patterns you notice — this helps your GP assess the cause.
Ready to take control of your weight loss journey?
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