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 Eggy Burps — What You Need to Know
Eggy burps (sulphur burps) are a gastrointestinal side effect some people experience when taking Mounjaro (tirzepatide) for weight management. This happens because Mounjaro slows how quickly food moves through your stomach, which can cause gas build-up and an unpleasant taste. It's usually temporary and manageable. Here's what the NHS and clinical evidence tell us about this side effect, how common it is, and what you can do about it.
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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 Eggy Burps
Mounjaro is a GIP and GLP-1 receptor agonist — meaning it activates two hormone pathways in your gut. One key effect is delayed gastric emptying: food moves more slowly from your stomach into your small intestine. This slower digestion can cause food to ferment in your stomach, producing hydrogen sulphide gas, which creates the distinctive eggy or sulphur smell.
This side effect is most common in the first 4–8 weeks of treatment, particularly when starting or increasing your dose. As your body adjusts to the medication, the effect often reduces. The gas build-up also happens because Mounjaro reduces overall appetite, so you may eat differently or less frequently, which can alter your digestive rhythm.
Importantly, this is not a sign that Mounjaro is harming you — it's a temporary adjustment as your GI system adapts. Clinical trials showed that this side effect typically resolves within weeks to months as your body acclimatises to the medication.
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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 Eggy Burps — Practical Tips
Dietary changes: Avoid foods that increase gas production (beans, cruciferous vegetables, carbonated drinks, fatty or greasy foods). Eat smaller, more frequent meals rather than large portions. Stay hydrated with water rather than fizzy drinks.
Timing and lifestyle: Eat slowly and chew food thoroughly. Light exercise after eating can aid digestion. Ginger tea or peppermint tea may help settle your stomach naturally.
When to contact your GP: If eggy burps persist beyond 8 weeks, are severely affecting your quality of life, or occur alongside severe stomach pain, contact your GP. Your prescriber may adjust your dose or suggest additional support. You can also try our free GLP-1 weight loss calculator to understand how Mounjaro works and track your progress alongside managing side effects.
- 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 common are eggy burps on Mounjaro?
Eggy burps are a common but temporary side effect, particularly in the first 4–8 weeks of treatment or after dose increases. Clinical trials reported this as a frequently reported GI symptom. Frequency and severity vary between individuals — some people experience mild occasional burps, others notice it more frequently. It typically improves as your body adjusts.
Are eggy burps dangerous or a sign something is wrong?
No. Eggy burps are not dangerous and do not indicate that Mounjaro is harming you. They result from slower stomach emptying and food fermentation — a normal physiological response. However, if you experience severe abdominal pain alongside eggy burps, contact your GP immediately, as this could indicate pancreatitis or another serious condition requiring urgent assessment.
Will eggy burps go away on their own?
Yes, in most cases. As your body adapts to Mounjaro over weeks to months, gastric emptying typically normalises and eggy burps usually resolve. If they persist beyond 8 weeks or significantly impact your quality of life, discuss this with your prescriber — they may adjust your dose or offer additional support.
What's the difference between Mounjaro and Wegovy for side effects like this?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whereas Wegovy (semaglutide) is a GLP-1 agonist only. Both slow gastric emptying and can cause eggy burps, nausea, and other GI side effects. Mounjaro's dual mechanism may produce different GI patterns in some individuals. Ask your GP which is more suitable for your circumstances.
Should I stop taking Mounjaro if I get eggy burps?
Do not stop taking Mounjaro without consulting your prescriber. Eggy burps are a temporary side effect, not a reason to discontinue. If the symptom is severely affecting you, your GP can discuss managing it through diet, timing of doses, or adjusting your treatment plan. Never change or stop your prescription without professional guidance.
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