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 Burping and Gas?
Burping and excess gas are not officially listed as common side effects of Mounjaro (tirzepatide) in the UK product information, but some people report bloating or digestive changes when taking this prescription injection. These effects are typically temporary and related to how Mounjaro slows stomach emptying. Most burping or gas resolves within the first few weeks as your body adjusts, though individual experiences vary. If you're experiencing persistent or severe digestive discomfort, your GP or the prescriber who issued your tirzepatide can offer personalised advice.
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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 Affects Your Digestive System
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by slowing gastric emptying — how quickly food moves from your stomach into your small intestine. This slower digestion can lead to bloating, gas, or burping as food sits in your stomach longer than usual. This effect typically decreases over time as your body adapts to the medication, usually within 4–8 weeks. The most commonly reported digestive side effects of tirzepatide are nausea, diarrhoea, constipation, and stomach pain — all listed in the UK prescribing information. Burping or excess gas may occur alongside these but is not formally classified as very common or common in clinical trials. If you're noticing increased gas or bloating after starting your Mounjaro KwikPen, it's worth keeping a simple food diary to identify whether certain foods trigger the symptoms.
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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.
When to Contact Your GP or Prescriber
Most digestive side effects of tirzepatide, including mild burping or bloating, settle within the first 4–8 weeks as your body adjusts. However, contact your GP or the prescriber who issued your Mounjaro if you experience: severe, persistent stomach pain (especially pain spreading to the back, which may indicate pancreatitis), vomiting that prevents you eating or drinking, or any side effect that significantly affects your daily life. You should also seek urgent medical attention if you develop signs of a serious allergic reaction or gallbladder problems. Never stop taking your tirzepatide without medical guidance — your prescriber can adjust your dose, suggest dietary changes, or discuss whether this medication remains suitable for you.
- 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 burping a normal side effect of Mounjaro?
Burping is not officially listed as a common side effect in UK prescribing information for tirzepatide, but some people report bloating or gas. These are likely related to slower stomach emptying. Most digestive changes resolve within 4–8 weeks as your body adapts to the medication.
What are the most common Mounjaro side effects in the UK?
Very common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain. These occur in more than 1 in 10 people. Injection site reactions, indigestion, and fatigue are also reported. All side effects should be discussed with your prescriber.
How long do digestive side effects last with Mounjaro?
Most digestive side effects, including bloating and gas, typically improve within 4–8 weeks as your body adjusts to tirzepatide. If symptoms persist beyond this period or worsen, contact your GP or prescriber for personalised advice.
Can dietary changes help reduce burping on Mounjaro?
Yes, eating smaller, more frequent meals and avoiding carbonated drinks, high-fat foods, and high-fibre foods may help reduce gas and bloating whilst taking tirzepatide. Keep a food diary to identify triggers and discuss dietary strategies with your prescriber.
How does Mounjaro compare to Wegovy for digestive side effects?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) slow stomach emptying, so both may cause digestive changes. Mounjaro uses a dual GIP and GLP-1 mechanism, whilst Wegovy is a GLP-1-only medication. Individual experiences vary, and your prescriber can discuss which is more suitable for you.
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.