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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Does Mounjaro Cause Bloating?
Bloating is a common side effect reported by people taking Mounjaro (tirzepatide) in the UK. While not everyone experiences it, understanding what causes bloating, how long it typically lasts, and when to seek GP advice can help you manage this effect. Mounjaro works by slowing how quickly food moves through your stomach, which can contribute to feelings of fullness and abdominal bloating, particularly in the first few weeks of treatment. This guide explains bloating in the context of UK NHS prescribing and what you can do about it.
10,000+ calculations today ยท NHS-aligned thresholds ยท 100% free
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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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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.
What Causes Bloating on Mounjaro?
Bloating on Mounjaro occurs primarily because tirzepatide slows gastric emptying โ the rate at which food leaves your stomach. This mechanism, while helpful for appetite control, can cause a feeling of fullness and abdominal distension, especially after eating. Additionally, Mounjaro may reduce overall food intake, which can lead to constipation in some people, and constipation often triggers bloating sensations.
Bloating is typically more pronounced during the first 4โ8 weeks of treatment or when your dose increases. Many people find that as their body adjusts to the medication โ and as they adapt their eating habits โ bloating improves significantly. Your dose titration schedule with Mounjaro (starting at 2.5 mg and increasing every 4 weeks) means you may experience bloating at each escalation point.
- Slowed stomach emptying due to GLP-1/GIP receptor activation
- Reduced food intake leading to digestive changes
- Constipation or irregular bowel movements
- Eating too quickly or large portions despite reduced appetite
- Carbonated drinks and high-fat foods can worsen bloating
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 โ all stored privately in your browser.
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Managing Bloating and When to Contact Your GP
Practical steps to reduce bloating include eating smaller, more frequent meals, chewing food thoroughly, and avoiding carbonated beverages and high-fat foods. Stay hydrated, include fibre-rich foods (gradually to avoid worsening constipation), and consider gentle movement like walking after meals.
Contact your GP if: bloating is severe, persistent beyond 8 weeks, accompanied by vomiting or severe stomach pain, or if you suspect signs of pancreatitis (pain spreading to the back). NHS specialist services monitoring your Mounjaro UK prescription can also advise on whether dose adjustment or additional support is needed. You can use our free BMI calculator and GLP-1 weight loss calculator to track how Mounjaro affects your overall health metrics alongside symptom management.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 a common side effect of Mounjaro in the UK?
Yes. Bloating is listed as a common side effect affecting up to 1 in 10 people taking tirzepatide. It's often associated with the medication's mechanism of slowing stomach emptying. Most people find it improves within the first 8 weeks as their body adjusts, though individual experiences vary.
How long does Mounjaro bloating typically last?
Bloating is usually most noticeable in the first 4โ8 weeks of treatment or after dose increases. For many people, it improves as their body adapts. However, if bloating persists beyond 8 weeks, discuss this with your GP or the NHS specialist service prescribing your tirzepatide.
Can I reduce bloating while taking Mounjaro?
Yes. Eat smaller, more frequent meals; chew thoroughly; avoid carbonated drinks and high-fat foods; stay hydrated; and include gentle physical activity. If you're also experiencing constipation, gradually add fibre-rich foods. Your prescriber can advise on whether additional support is needed.
What's the difference between Mounjaro and Wegovy regarding bloating?
Both are GLP-1 agonists with similar side effects including bloating. Mounjaro is a dual GIP/GLP-1 agonist and may have a different profile, but bloating remains common with both. Individual responses vary, and any concerns should be discussed with your GP or prescriber.
When should I contact my GP about Mounjaro bloating?
Contact your GP if bloating is severe, persistent beyond 8 weeks, accompanied by vomiting or severe stomach pain, or if you suspect pancreatitis (pain radiating to the back). Your NHS specialist weight management service can also advise on whether dose adjustment or alternative approaches are appropriate.
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.