Why sulphur burps happen on Mounjaro — and what the evidence tells us

What gastric emptying has to do with the smell

The SURMOUNT-1 trial, published in the New England Journal of Medicine, documented gastrointestinal symptoms as the most common class of adverse events across all tirzepatide doses. Nausea, vomiting, diarrhoea and burping were each recorded in a meaningful proportion of participants, and the pattern was consistent: symptoms peaked in the early weeks and after each dose increase, then typically eased. Sulphur burps sit within this wider picture.

Tirzepatide works partly by activating GIP and GLP-1 receptors that govern how quickly the stomach empties into the small intestine. Slow gastric emptying is not a side effect in the incidental sense, it is part of how the medicine reduces appetite. Food lingers. Proteins, particularly those containing sulphur amino acids such as methionine and cysteine, remain in the upper gut longer than they normally would. The resident bacterial populations there have more time and substrate to work with, and hydrogen sulphide is one of the gases they produce as a by-product.

If you are curious about why you get sulphur burps on Mounjaro and want a closer look at the mechanism behind them, that page walks through the chemistry in detail. The smell is not a sign of infection or a dangerous reaction, it is chemistry, predictably following from the medicine's mechanism. You can read more about the broader range of tirzepatide's gastrointestinal effects on our Mounjaro side effects page.

Why dose increases tend to bring sulphur burps back

One pattern that many people on tirzepatide notice is that sulphur burps settle after a few weeks at a given dose, then return when the dose steps up. This tracks exactly with what the SURMOUNT programme data showed: GI events are tied to the pharmacological stimulus on the gut, and increasing that stimulus (moving from 5mg to 7.5mg, for instance) resets the clock.

The starter dose of 2.5mg exists primarily to let the body adjust to tirzepatide's effect on gastric motility before the therapeutic doses begin. That adjustment period is real, but it does not fully insulate against GI symptoms later; each titration step introduces a fresh period of adaptation. Knowing this in advance matters, because people who expect sulphur burps to disappear permanently after the first month are sometimes caught off guard when a dose change brings them back.

The good news is that the rebound is almost always shorter than the original episode. The gut is already partially adapted to slower emptying; it needs less time to settle at the new level. More detail on this pattern is available if you want to understand what to expect across a full titration schedule.

Foods that make it worse, and practical steps worth trying

The food you eat directly determines how much sulphur-containing substrate is available for bacterial fermentation. High-sulphur foods include eggs, cruciferous vegetables (broccoli, cabbage, cauliflower, Brussels sprouts), garlic, onions, meat, and some dairy products. None of these need to be eliminated permanently, but reducing them during the early weeks of a new dose can noticeably reduce sulphur burp frequency for many people.

Eating smaller portions, more slowly, also helps. One thing prescribers hear regularly is that people on tirzepatide underestimate how much the medicine reduces their stomach's capacity, and eating at their previous pace leads to pooling of food and gas. Staying well hydrated supports gut motility. Fizzy drinks can compound the problem, they add gas to an already-slowed system.

Some people find that peppermint tea or ginger settles things. Neither has strong clinical evidence specifically in the context of GLP-1 medicines, but both have a reasonable basis in general GI physiology and carry little risk. If sulphur burps are persistent, severe, or accompanied by other symptoms (particularly any significant pain) speak to your prescriber rather than waiting it out. Our guide to managing sulphur burps on Mounjaro covers these strategies in more depth, including when to make contact.

For broader context on how Mounjaro works and what the treatment journey looks like, the Mounjaro overview page is a good starting point. If you are thinking about what private treatment costs and what those costs cover, the Mounjaro cost page sets that out plainly. And if you are weighing up all the options available to you, our weight-loss treatment overview gives the wider picture.

If you are ready to speak to a prescriber about starting treatment, or want clinical advice on a symptom you have been experiencing, you can start your free consultation and a GPhC-registered Independent Prescriber will review it the same day.