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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Mounjaro and Trapped Wind: What You Need to Know
Trapped wind (abdominal bloating and gas) is a common side effect experienced by people taking Mounjaro (tirzepatide), especially during the first few weeks of treatment or when increasing your dose. This is because Mounjaro slows how quickly food moves through your digestive system. The good news is that for most people, trapped wind and bloating typically improve over time as your body adjusts to the medication. Understanding what to expect and how to manage it can help you stay comfortable while your body adapts to this prescription-only weight management injection.
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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.
Why Mounjaro Causes Trapped Wind and Bloating
Mounjaro is a dual GIP and GLP-1 receptor agonist — this dual mechanism is what sets it apart from single-action medications like Wegovy (semaglutide). When you start tirzepatide, it activates both GIP and GLP-1 pathways, which slow gastric emptying (how fast food leaves your stomach) and reduce how much you eat. This slower digestion is intentional and helps with weight management, but it can also cause bloating, excess gas, and that uncomfortable trapped wind sensation.
The effect is typically strongest when you start Mounjaro or increase your dose. Many people also experience constipation or diarrhoea alongside trapped wind — these are very common gastrointestinal (GI) side effects listed in the official patient information. As your digestive system adjusts over weeks 2–4, these symptoms usually ease. However, some people experience persistent bloating throughout their treatment.
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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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Managing Trapped Wind While Taking Mounjaro
Several practical steps may help reduce trapped wind and bloating:
- Eat slowly and chew thoroughly — smaller bites reduce air swallowing and support the slower digestion Mounjaro creates
- Avoid carbonated drinks — fizzy drinks introduce more gas into your digestive system
- Stay hydrated with water — adequate fluid intake supports healthy digestion
- Eat smaller, more frequent meals — this aligns with how Mounjaro reduces appetite and minimises digestive strain
- Avoid high-fat and high-fibre foods initially — these are harder to digest and may worsen bloating
- Walk after meals — gentle movement aids digestion
If bloating persists beyond week 4 or becomes severe, speak to your GP or the prescriber who issued your Mounjaro prescription.
- 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.
How long does trapped wind last when you start Mounjaro?
Trapped wind and bloating typically peak in the first 1–2 weeks and improve significantly by week 4 as your body adjusts. Some people experience ongoing mild bloating, but severe symptoms usually settle. If bloating persists beyond 4 weeks, contact your GP for advice.
Is trapped wind a sign Mounjaro isn't working?
No. Trapped wind is a normal side effect of how Mounjaro works — it slows digestion intentionally to help with appetite control and weight management. It's not a sign of a problem, but if it's severe or distressing, speak to your healthcare provider.
Can you take anything to relieve trapped wind while on Mounjaro?
Over-the-counter remedies like simethicone (Infacol, Buscopan IBS Relief) may help reduce bloating. Peppermint tea can also soothe digestion. Always check with your GP or pharmacist before taking any new medication or supplement alongside Mounjaro, as it may affect absorption of oral medicines.
Should I stop Mounjaro if I have severe trapped wind?
Don't stop without medical advice. Severe bloating or persistent GI symptoms warrant a conversation with your prescriber — they may adjust your dose, suggest management strategies, or discuss whether Mounjaro is right for you. Never stop a prescription injection without guidance.
Does trapped wind happen with every Mounjaro dose increase?
Many people experience mild bloating when moving to a higher dose, though it's usually less severe than at the start. This typically settles within 1–2 weeks. Sticking to the dose titration schedule (minimum 4 weeks between dose increases) gives your body time to adjust and often reduces side effects.
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.