Have you recently started Mounjaro and found yourself dealing with unexpected and uncomfortable belching that smells a bit like rotten eggs? If so, you're not alone - and you're certainly not imagining it. These “sulphur burps” can be distressing, especially when you're otherwise motivated and hopeful about your weight loss journey.
Based on a survey in the UK, many patients reported that they felt blindsided by this peculiar side effect. One minute, they’re feeling hopeful with a powerful new weight loss injection, and the next, they’re wondering if something’s gone wrong with their digestive system. And perhaps you're wondering the same - Is this normal? Will it go away? And what can I do about it?
This guide was created to address those very concerns. We’ll explore why Mounjaro (tirzepatide) might cause sulfur burps, how common and manageable this issue is, and what you can do to ease the discomfort without compromising your progress. Let's unpack the science behind it and, more importantly, the practical ways to feel better.
Mounjaro has quickly become one of the most talked-about advances in the treatment of obesity and type 2 diabetes. Approved by MHRA, it has brought fresh hope to individuals struggling with weight loss and metabolic health.
Its arrival on the NHS and in private weight loss clinics has been met with enthusiasm, especially because of its dual-action mechanism that promotes both improved blood sugar control and significant weight loss. For many, it offers the possibility of reclaiming health, mobility, and confidence.
But with all medications, especially newer ones, there can be surprises. One of these is gastrointestinal discomfort, and in particular, foul-smelling burps that some describe as tasting or smelling like sulphur. While not dangerous, they can be off-putting and even socially disruptive.
To understand why such a symptom might occur, it helps to know a bit about how Mounjaro functions in the body. Tirzepatide is what we call a dual incretin agonist. It mimics the actions of two naturally occurring gut hormones - GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Together, these hormones help regulate blood sugar after eating, reduce appetite, and, importantly, slow down how quickly food moves through the stomach.
This slowing down of digestion is beneficial for weight loss, as it helps you feel fuller for longer and keeps post-meal blood sugars steady. But it can also lead to side effects, including nausea, bloating, and in some cases, excessive or unpleasant-smelling burping.
Mounjaro is approved for use in adults with type 2 diabetes and weight loss in individuals with a BMI of 30 or more, or 27 with weight-related health conditions. It should always be prescribed and monitored by a qualified healthcare professional who can guide you through its benefits and potential challenges.
Sulphur burps - sometimes called rotten egg burps - occur when gas containing hydrogen sulfide is released from the stomach and expelled through belching. The smell is distinctive and often compared to decaying eggs. It's not harmful in small amounts, but it can be unpleasant and, for some, embarrassing.
Patients describe them as sudden, foul-smelling belches that seem to come out of nowhere, sometimes accompanied by a sour or metallic taste. They can happen after meals or even on an empty stomach, and in some cases, they disrupt sleep or social activities.
Although they aren’t included as a common side effect in Mounjaro’s official safety profile, reports of sulphur burps have emerged among users, particularly those in online forums, weight loss support groups, and anecdotal clinic feedback. While not everyone will experience them, they are a recognised concern and likely tied to how the medication alters digestion.
One of Mounjaro’s main effects is slowing gastric emptying. That means food stays in your stomach and upper digestive tract longer than usual. While this helps you feel full and eat less, it also gives gut bacteria more time to break down the food, especially proteins and certain carbohydrates. When this bacterial fermentation happens, it can release gases like methane, hydrogen, and hydrogen sulfide.
Hydrogen sulfide is the culprit behind the rotten egg smell. The risk of producing this gas increases if your diet contains a lot of high-sulphur foods - think eggs, onions, garlic, cruciferous vegetables like cabbage and broccoli, red meats, and certain dairy products. Add in high-fat meals, which can slow digestion even further, and the stage is set for fermentation and gas production.
It's also important to note that every individual has a unique gut microbiome. Some people naturally have more sulphur-producing bacteria, which might explain why only certain individuals experience this side effect on Mounjaro, even when eating similar diets.
If you’re dealing with sulphur burps while taking Mounjaro, you don’t need to suffer in silence. There are several practical ways to ease the issue without having to stop the medication.
Similarly, opting for lighter, lower-fat meals can support faster digestion. Eating smaller meals more frequently throughout the day may prevent your stomach from becoming overly full and reduce the fermentation time.
If dietary changes and mindful eating don’t fully resolve the issue, certain over-the-counter remedies may offer relief, but they should be used with guidance from your pharmacist or GP.
Simethicone-based products such as Wind-eze can help break up gas bubbles in the gut, making it easier for your body to expel them naturally. It also comes in our SheMed support pack.
Some people find benefit in taking probiotics, which can help rebalance gut bacteria. Not all probiotic strains are effective for this purpose, so look for ones supported by evidence in digestive health - your pharmacist or dietitian can recommend appropriate UK-approved brands.
Another option is bismuth subsalicylate (like Pepto-Bismol), which can bind to hydrogen sulfide and neutralise the smell. However, this should only be used occasionally and with medical guidance, especially if you’re on other medications, as it can interact with drugs.
Activated charcoal is sometimes suggested, but it can also bind to medications and nutrients, interfering with absorption. It's best to approach this option cautiously and only after speaking with your doctor.
While sulphur burps are usually a benign and manageable side effect, there are situations where you should seek medical advice. If your symptoms become persistent, worsen over time, or start to impact your daily life, speak to your GP or prescribing clinician. You may need a review of your dosage, further dietary support, or even a check for other digestive issues such as gastritis or bacterial overgrowth.
In some cases, sulphur burps could be a sign of an underlying gastrointestinal condition, particularly if they’re accompanied by red flag symptoms like severe abdominal pain, ongoing nausea or vomiting, diarrhoea or constipation, fever, unexplained weight loss, or blood in your stool or vomit.
Don’t wait to report these symptoms. Mounjaro may need to be paused or adjusted, and your doctor can ensure there’s nothing more serious occurring in the background.
Starting Mounjaro is a significant and often hopeful step in addressing weight or metabolic health challenges. While it can come with surprises like sulphur burps, it’s important to remember that most side effects are manageable - and often temporary. You don’t have to choose between relief and results.
With the right strategies, support, and awareness, you can continue progressing on your weight loss journey without being held back by uncomfortable symptoms. Stay in regular touch with your healthcare team.
Don’t hesitate to ask questions or voice concerns, especially about digestive side effects. You are not alone, and your concerns are valid. Mounjaro is one tool in a broader toolkit that includes lifestyle changes, nutrition, movement, and mental well-being. Together, these elements can help you achieve your goals in a sustainable, empowered way.
FAQs
While not officially listed as a common side effect in clinical trials, sulphur burps have been reported by some Mounjaro users. They are likely linked to the way the medication slows digestion, which can increase gas production in the gut. The symptom is usually manageable and not harmful.
Reducing foods high in sulphur - like eggs, onions, garlic, cabbage, broccoli, and red meat - may help. Limiting high-fat meals and fizzy drinks can also reduce burping. Keeping a food diary can be useful for identifying personal triggers.
Not usually. Most cases improve with dietary changes and supportive measures. However, if the symptoms are severe, persistent, or affecting your quality of life, speak to your prescribing doctor. They may suggest adjustments or further assessment.