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
Free tracker included with every download this week
Why Am I Bloated on Mounjaro?
Bloating is a common side effect when taking Mounjaro (tirzepatide) for weight management in the UK. It typically occurs because Mounjaro slows how quickly food moves through your digestive system, which can cause temporary abdominal discomfort and a feeling of fullness. For most people, bloating improves as your body adjusts to the medication over the first few weeks. Understanding what's happening and knowing when to seek help from your GP is important for managing this side effect safely.
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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 Causes Bloating and When to Expect Relief
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by slowing gastric emptying — the speed at which your stomach empties food into the small intestine. This effect, combined with reduced appetite, helps support weight loss. However, slower digestion can trap gas in your digestive system, causing bloating, stomach discomfort, and a feeling of fullness even when you haven't eaten much.
Bloating typically peaks during dose titration (when increasing your dose every 4 weeks) and often improves within 3–7 days as your body adapts. Some people experience ongoing mild bloating, whilst others find it resolves completely. The severity varies — factors like diet, hydration, and individual sensitivity affect how much bloating you notice.
- Bloating is listed as a "common" side effect (affecting up to 1 in 10 people)
- It's usually worse in the first 4–8 weeks of treatment
- Most people report improvement with dose adjustments and dietary changes
- Persistent severe bloating should be discussed with your GP or prescriber
Clinically BackedWeight Loss
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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.
Managing Bloating and When to Contact Your GP
To reduce bloating on Mounjaro, eat smaller, frequent meals and avoid foods that produce excess gas — such as beans, lentils, carbonated drinks, and cruciferous vegetables. Staying well hydrated, moving regularly (gentle walking aids digestion), and eating slowly can help. If bloating is severe, persistent, or accompanied by severe stomach pain spreading to your back, contact your GP immediately as this could indicate pancreatitis — a serious condition requiring urgent assessment.
If you're finding bloating significantly affects your quality of life, your prescriber may adjust your Mounjaro dose or suggest a slower titration schedule. Never stop taking Mounjaro without discussing this with your prescriber first. Use our free GLP-1 weight loss calculator to understand how Mounjaro works alongside lifestyle changes for sustainable results.
- 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 bloating on Mounjaro normal?
Yes, bloating is a common side effect of Mounjaro, affecting up to 1 in 10 people. It occurs because Mounjaro slows how quickly food moves through your digestive system. Most people find bloating improves within the first few weeks as their body adjusts to the medication.
How long does bloating last on Mounjaro?
For most people, bloating is worst during the first 4–8 weeks and improves significantly as the body adapts. Some experience relief within days of starting a new dose, whilst others notice gradual improvement over 2–3 weeks. If bloating persists beyond 8 weeks, discuss this with your GP.
What can I do to reduce bloating on Mounjaro?
Eat smaller, frequent meals, avoid gas-producing foods (beans, fizzy drinks, cruciferous vegetables), drink plenty of water, and move gently after eating. Eating slowly and chewing thoroughly also helps. If bloating is severe, your prescriber may adjust your dose schedule.
When should I contact my GP about bloating on Mounjaro?
Contact your GP if bloating is severe, persistent beyond 8 weeks, or accompanied by severe stomach pain spreading to your back (which could indicate pancreatitis). Your GP can assess whether any adjustments are needed or if the medication is right for you.
Does bloating mean Mounjaro isn't working?
No — bloating is a side effect of how Mounjaro works (slowing digestion) and is separate from its weight loss effects. Many people experience bloating and still lose weight successfully. If you have concerns about weight loss progress, use our free GLP-1 calculator and discuss results with your prescriber.
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.