Mounjaro sulphur burps and diarrhoea: why they happen and how to manage them

You burped, it smelled like eggs, and nobody warned you about this

It catches people off guard. Nausea gets mentioned at the start, and sulphur burps on Mounjaro get far less attention than they deserve. The mechanism is the same as the one behind Mounjaro's weight-loss effect: by activating GIP and GLP-1 receptors, tirzepatide slows gastric emptying so that food sits in the stomach longer. While it is sitting there, sulphur-containing compounds in everyday foods (eggs, onions, garlic, broccoli, red meat) are broken down more extensively, and the resulting hydrogen sulphide gas has nowhere to go but up. The burps are not dangerous. They are, however, a reliable sign that your gut is still adjusting to the slowed transit. Many people find the eggy burping is worst in the first week or two after starting a new dose, then quiets down. If yours have not settled after three to four weeks at the same dose, that is worth raising with your prescriber rather than simply waiting. Keeping your injection pen in the fridge door rather than at the back means you will notice it each time you go for something to eat, a useful prompt to log whether your symptoms are improving week on week. The fuller picture of gut-related side effects is covered on our Mounjaro side effects overview if you want to understand how the different symptoms relate to each other.

Why diarrhoea happens alongside the burps, and what helps

Our page on sulphur burps and diarrhea with Mounjaro explains why these two symptoms often arrive together, as both are downstream of the same change in gut motility. When gastric emptying slows, the pattern of movement through the intestines can become irregular, the bowel sometimes overcompensates and rushes contents through faster than usual, producing loose or watery stools. For others, the issue is more about fat malabsorption: because food transits differently, fatty foods in particular can trigger diarrhoea. The practical steps that reduce both symptoms overlap: smaller meals eaten slowly, reducing high-fat and high-sulphur foods for a few weeks, cutting back on alcohol, and keeping hydrated with plain water across the day. The Mounjaro and diarrhoea page goes into more detail on the bowel side of this if diarrhoea is your main concern. Probiotic-rich foods such as yoghurt or kefir are not harmful and some people report they help, though evidence for this specifically in GLP-1 users is limited, and your prescriber or a registered dietitian is the right person to advise on dietary changes tailored to you. Antidiarrhoeal medicines are sometimes used short-term; again, check with a clinician before starting them on Mounjaro.

When to get medical help, and when sulphur burps and diarrhoea become a red flag

Most of the time these symptoms are an inconvenience, not a danger, though our page covering sickness and diarrhoea on Mounjaro sets out the circumstances where you need to seek medical help promptly. Severe or persistent diarrhoea lasting more than a few days can cause dehydration serious enough to affect kidney function, watch for signs such as very dark urine, dizziness on standing, or a significant drop in how much you are urinating. Those warrant a call to your GP or NHS 111 the same day. Separately, pay attention to the nature of any stomach pain. Diarrhoea plus mild cramping is typical; severe, persistent stomach pain that spreads towards the back, with or without vomiting, is a different matter. The MHRA highlighted acute pancreatitis as a known (and infrequently occurring, but serious) side effect of GLP-1 medicines in a Drug Safety Update published in January 2026. That symptom profile is a reason to stop the injection and get assessed urgently, not to manage it at home. If you experience an allergic reaction (rash, swelling, difficulty breathing), treat it as an emergency. For side effects that are unpleasant but not urgent, the right route is your prescriber. You can also report any suspected side effect from Mounjaro directly using the MHRA's Yellow Card scheme, patient reports genuinely contribute to post-market safety monitoring for medicines with Black Triangle status like tirzepatide. If you are unsure whether what you are experiencing counts as urgent, contact us via our aftercare team, available seven days a week.

Getting the consultation right if side effects are affecting your treatment

Sulphur burps and diarrhoea that persist past the adjustment period, or that are severe enough to affect how you eat or how you live, are worth a proper clinical conversation, not just a Google. Prescribers can consider whether a dose adjustment is appropriate, whether the titration schedule needs slowing, or whether there is something in your current medication list or diet that is making symptoms worse. At nume, our prescribers review every repeat order clinically before it is dispensed; side effects are a routine part of that conversation, not an awkward add-on. If your symptoms are troubling you between orders, you can reach the team through our contact page without waiting for a repeat cycle. For a broader sense of how Mounjaro works and what it is used for, the Mounjaro treatment overview covers the full picture. And if you are still considering whether treatment is right for you, starting a free consultation is where that assessment begins, our prescribers discuss suitability and side effects together, so you go in with clear expectations rather than unpleasant surprises.