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 Eggy Burps — A UK Health Guide
Eggy burps (sulphur-smelling belches) are a potential side effect some people experience while taking Mounjaro (tirzepatide). This happens because Mounjaro slows how quickly food moves through your stomach, which can change how your gut bacteria break down food. While uncomfortable, this is usually temporary and manageable. Understanding what causes it and how to reduce it can help you feel more confident managing this side effect. Use our free GLP-1 weight loss calculator to explore how Mounjaro works alongside lifestyle changes.
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Calculate Your BMI Instantly
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.
Why Does Mounjaro Cause Eggy Burps?
Eggy burps occur because Mounjaro slows gastric emptying — the rate at which food leaves your stomach and enters the small intestine. This is actually part of how Mounjaro helps with weight management, but the delayed digestion can cause hydrogen sulphide gas to build up in your digestive system, which smells like rotten eggs.
When you eat protein-rich foods, your gut bacteria ferment the food more slowly, producing sulphur compounds. Mounjaro amplifies this effect because food stays in your stomach longer than usual. This is most common in the first few weeks as your body adjusts to the medication, and typically improves or disappears as you continue treatment. The effect also tends to reduce over time because your stomach adapts to the medication's effects.
- More common at higher doses (10 mg and above)
- Often worse after eating protein-heavy meals
- Usually subsides after 4–8 weeks of treatment
- Not dangerous — just uncomfortable and embarrassing
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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.
How to Manage Eggy Burps on Mounjaro
Practical steps can significantly reduce eggy burps: eat smaller, more frequent meals rather than large portions; chew food thoroughly to aid digestion; avoid sulphur-rich foods like eggs, cabbage, broccoli, and onions; drink plenty of water to support digestion; and eat slowly. Some people find that taking a digestive enzyme supplement or probiotic helps, though evidence is mixed — ask your prescriber before starting any new supplement. Ginger tea or peppermint tea may also help settle your stomach. Most importantly, this side effect is temporary and not a reason to stop your medication — mention it to your healthcare provider if it's significantly affecting your quality of life.
- 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 eggy burps a sign that Mounjaro isn't working?
No. Eggy burps are a side effect caused by slower digestion, not a sign of ineffectiveness. In fact, the slowed stomach emptying that causes them is part of how Mounjaro helps with weight management. It's an uncomfortable but harmless side effect that typically improves over time.
How long do eggy burps last on Mounjaro?
Most people find eggy burps improve after 4–8 weeks as their body adjusts to the medication. Some experience them throughout treatment but find them less severe. If they persist beyond 12 weeks, discuss this with your prescriber — they may adjust your approach or recommend other strategies.
Can I prevent eggy burps when starting Mounjaro?
You can't completely prevent them, but you can reduce their severity by eating smaller meals, avoiding sulphur-rich foods, drinking plenty of water, and chewing slowly. Starting at the lowest dose (2.5 mg) and increasing gradually also gives your body time to adjust, which may help.
Are eggy burps more common with Mounjaro than Wegovy?
Eggy burps can occur with both Mounjaro and Wegovy since both slow digestion. However, they may be slightly more common with Mounjaro because it's a more potent dual GIP and GLP-1 agonist. Individual experiences vary significantly, and timing matters — they're often worse in early weeks.
Should I stop Mounjaro if I get eggy burps?
No — eggy burps are not a serious side effect and don't mean you should stop treatment. They're uncomfortable but temporary and manageable. Discuss persistent symptoms with your GP or prescriber. They can suggest strategies or, rarely, adjust your dose if other side effects are also concerning.
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.