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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Egg Burps On Mounjaro — Why This Happens
Egg burps (sulphur-smelling burps) are a reported side effect of Mounjaro that some people experience, particularly in the early weeks of treatment. This distinctive burp is caused by how tirzepatide affects digestion and stomach emptying. While unpleasant, egg burps are typically temporary and often improve as your body adjusts to the medication. Understanding why this happens and what to expect can help you manage the experience while using Mounjaro, the dual GIP and GLP-1 receptor agonist injection licensed for weight management in the UK.
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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.
What Causes Egg Burps On Mounjaro?
Egg burps occur because Mounjaro (tirzepatide) slows how quickly food moves through your stomach—a process called delayed gastric emptying. When food stays in your stomach longer, it ferments slightly, producing sulphur-containing gases. These gases are then released as burps with a distinctive egg-like or rotten smell.
This effect is most noticeable:
- In the first 4–8 weeks of starting Mounjaro or increasing your dose
- After eating protein-rich foods (eggs, meat, fish, dairy)
- When you eat larger portions before your body has fully adjusted
- If you consume food high in sulphur compounds (broccoli, onions, garlic)
As your body adjusts to tirzepatide and gastric emptying normalises over time, egg burps typically decrease significantly. The mechanism responsible for slowing digestion also contributes to the appetite-suppressing effect that helps with weight management, which is why this side effect is a natural part of how the medication works.
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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 Egg Burps and When to Seek Help
Most people find egg burps manageable with simple dietary adjustments. Eat smaller, more frequent meals; avoid large portions at once. Choose foods lower in sulphur (white fish, chicken breast, pasta, rice) rather than cruciferous vegetables or heavily seasoned foods. Stay hydrated and take your time eating—rushing can worsen the effect.
Egg burps usually resolve within a few weeks as your digestive system adapts. However, if the symptom persists beyond 8 weeks, severely impacts your quality of life, or is accompanied by persistent nausea or stomach pain, contact your GP. They can advise whether continuing Mounjaro is right for you or whether dose adjustment might help. Track any changes alongside other side effects using our free progress tracker to help identify patterns and report accurately to your healthcare provider.
- 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 do egg burps last on Mounjaro?
Egg burps typically improve within 2–8 weeks as your body adjusts to how tirzepatide affects digestion. For most people they become much less noticeable or disappear entirely. If they persist beyond 8 weeks, discuss with your GP.
Are egg burps dangerous or a sign something is wrong?
No, egg burps are not dangerous. They're a known side effect caused by delayed gastric emptying from tirzepatide. They're unpleasant but harmless. However, if accompanied by severe stomach pain, persistent vomiting, or severe nausea lasting days, contact your GP as these could indicate pancreatitis.
Can I prevent egg burps on Mounjaro?
You can reduce egg burps by eating smaller meals, avoiding sulphur-rich foods (eggs, onions, garlic, broccoli), chewing thoroughly, and staying hydrated. These adjustments help digestion work more smoothly. Avoiding large portions is particularly effective.
Do egg burps mean Mounjaro isn't right for me?
No. Egg burps are a temporary side effect, not a sign the medication won't work. Many people experience them initially but find them manageable with dietary changes. Discuss with your prescriber if they significantly affect your wellbeing—they can advise on whether to continue.
What's the difference between egg burps on Mounjaro versus Wegovy?
Both tirzepatide (Mounjaro) and semaglutide (Wegovy) slow gastric emptying and can cause egg burps. Mounjaro uses a dual GIP and GLP-1 mechanism, while Wegovy is a GLP-1 agonist only. Reported side effect profiles are similar, though individual experiences vary.
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