Eggy burps and diarrhoea on Mounjaro: why they happen and what you can do

It's your third day on 2.5mg and the burps have arrived uninvited

You picked up your Mounjaro pen, noted its DPD tracking number, and gave yourself the first injection without drama. A few days later, the eggy burps started. Then loose stools. This is, frustratingly, a very common experience in the first one to two weeks of tirzepatide, not a sign that something has gone wrong, and not a reason to panic.

The mechanism is straightforward. Mounjaro slows the rate at which the stomach empties, which is partly how it reduces appetite. That slower transit means food (particularly high-protein and high-sulphur foods like eggs, red meat, cruciferous vegetables and onions) ferments for longer in the gut. The gas produced contains hydrogen sulphide, which is why the burps smell the way they do. The same delayed gastric emptying can shift fluid balance in the bowel and produce looser stools. For more detail on how this specific symptom cluster develops, the page on eggy burps on Mounjaro covers the mechanism in full.

Diarrhoea tends to be more common early in treatment or after a dose step-up. It's usually mild to moderate and resolves on its own. The clinical trials consistently showed GI effects were the most frequently reported side effects, most pronounced in the early weeks. If you're finding that sulphur burps and diarrhea are arriving together on Mounjaro, that combination is well documented and there are practical ways to manage it. Knowing that doesn't make it feel better on day three, but it does mean you have a reasonable basis for watching and waiting rather than immediately stopping treatment.

What actually makes a difference: practical adjustments that are worth trying

Small meals help more than almost anything else. Tirzepatide slows gastric emptying, so a large meal sits in the stomach longer and ferments more. Eating to 80% full (stopping before you feel stuffed) reduces both the belching and the downstream GI disruption. Eating slowly matters for the same reason.

Cutting back temporarily on the highest-offending foods can reduce the sulphur-burp intensity significantly. Eggs, garlic, onions, broccoli, cauliflower and red meat are all high in sulphur compounds; they're not bad foods, but during the adjustment period reducing portion sizes can make a noticeable difference. Reintroducing them gradually once the GI symptoms settle is usually fine.

Hydration is critical, especially if diarrhoea is present. Loose stools deplete fluid and electrolytes faster than most people realise. Water, diluted squash, and foods with high water content all count. Alcohol and carbonated drinks tend to worsen both symptoms and are worth avoiding in the early weeks.

If you're dealing with the combination of sulfur burps and diarrhea on Mounjaro, that page goes further on dietary strategies. If symptoms are making everyday life difficult, speak to your prescriber, there may be clinical reasons to slow the titration schedule rather than push through.

When to get medical help rather than wait it out

Most eggy burps and loose stools on Mounjaro are unpleasant but not dangerous. There are specific situations, though, where you should contact a doctor or call 111 promptly rather than managing at home.

Severe stomach pain (particularly pain that is persistent and radiates towards your back, with or without vomiting) should not be attributed to ordinary GI upset. In January 2026, the MHRA issued a Drug Safety Update specifically flagging acute pancreatitis as an infrequent but serious known risk with GLP-1 medicines; the MHRA Drug Safety Update series contains the full communication. Pancreatitis requires prompt medical assessment. More on protecting your digestive health during treatment is covered on the page about pancreas care on Mounjaro.

You should also seek medical help if diarrhoea is severe enough to prevent you from keeping fluids down, if you develop signs of dehydration (dizziness, reduced urination, dry mouth), or if symptoms persist for more than two weeks without any improvement.

Any suspected side effect (even one that seems minor) can be reported directly by patients and carers via the Yellow Card scheme. Reports help the MHRA monitor the safety of medicines in real-world use. It takes about ten minutes and you don't need a GP's help to submit one.

How a clinical prescriber approaches these symptoms before and during treatment

Eggy burps and diarrhoea are common enough that a thorough prescriber will often mention them before the first pen is used, not to alarm, but so patients know what to watch for versus what needs attention. At nume, every consultation is reviewed personally by a GPhC-registered prescriber, not processed by an algorithm. That means your full health picture is seen before treatment starts, including factors that might make GI side effects more likely or severe.

The broader side-effect profile of tirzepatide, including the full list of GI effects, is covered on the Mounjaro side effects page. If you're still at the research stage, the Mounjaro overview covers how the medicine works, what it's licensed for in the UK, and what the clinical evidence shows. For those ready to discuss suitability, the free consultation is the place to start, side effects, your medical history and how to reduce early GI symptoms are all part of the conversation, not afterthoughts.