Why Do You Get Sulfur Burps on a GLP-1?

Start with the word. Prescribing labels use eructation, the clinical term for belching, and none of the three labels checked for this page uses the phrase sulfur burps or records odor. The figures below therefore answer a narrower question than the one people search for: how often trial participants belched more than people on placebo.

The Wegovy label from Novo Nordisk, revised in June 2026 and published on DailyMed and the FDA's website, pools three 68-week placebo-controlled trials in adults with obesity or overweight. In its adverse-reaction table, eructation was reported by 7% of the 2,116 adults on Wegovy injection and by fewer than 1% of the 1,261 on placebo. In the single 68-week pediatric trial, the figures were 4% of 133 adolescents on Wegovy and 0% of 67 on placebo. The same label adds a sentence worth keeping: gastrointestinal reactions, eructation among them, "were most frequently reported during dosage escalation."

The Zepbound label from Eli Lilly, revised in August 2026, pools two placebo-controlled weight-reduction trials in adults with obesity or overweight, with or without type 2 diabetes. Eructation was reported by 4%, 5% and 5% of participants on the three maintenance doses, against 1% of the 958 on placebo. The Mounjaro label, revised August 2026, draws on a different population, 718 tirzepatide-treated adults with type 2 diabetes in two placebo-controlled trials, and lists eructation at 3.0%, 2.5% and 3.3% across the same three doses versus 0.4% on placebo.

Two cautions. The trial populations, durations and comparators differ, so the numbers are not a head-to-head between semaglutide and tirzepatide. And a label frequency is a floor, not a ceiling: a participant who belched more but never mentioned it to a study nurse is not in the table. The full label facts are in the reference entries for Wegovy, Zepbound and Mounjaro.

The labels are direct on mechanism. Section 12.2 of the Wegovy label states that semaglutide delays gastric emptying. The Zepbound and Mounjaro labels say the same of tirzepatide and add a detail that matters for anyone tracking symptoms: "The delay is largest after the first dose and this effect diminishes over time."

That is where the label stops. It does not explain why a belch smells of eggs, because no trial measured that. The explanation this page offers is its own inference, joining two sourced facts. First, food that sits in the stomach and upper gut for longer gives bacteria more time to work on it. Second, the rotten-egg smell is hydrogen sulfide, which gut bacteria produce from sulfur-containing compounds. A 2012 review by Carbonero and colleagues in Frontiers in Physiology describes sulfate-reducing bacteria as ubiquitous in the human intestinal mucosa and notes that organic sulfur compounds such as cysteine, taurocholic acid and mucin are a more efficient source of sulfide than inorganic sulfate, "with meat being a particularly important source."

Put together, the story is plausible: slower transit, longer fermentation, more hydrogen sulfide, and a belch that carries it upward. It is also a story, not a trial finding, and this page will not dress it up as one. What the label does support is the timing pattern people report: if the emptying delay peaks after a dose and fades, an odor that tracks the dose cycle fits the mechanism, which is exactly why dose day belongs in the log.

Because the mechanism runs through what bacteria are fed, most of the patterns people notice are dietary. None of the items below is a food to avoid on this page's authority; they are variables worth writing down so that a real pattern, if there is one, shows up in your own record.

Sulfur-rich foods come first. The Carbonero review names meat as a particularly important source of the organic sulfur compounds bacteria turn into sulfide, and lists commercial breads, dried fruits, vegetables, nuts, fermented beverages and brassica vegetables among sources of inorganic sulfate. Eggs, onions and garlic are the ones people mention most in their own notes. If the worst evenings follow a large steak or a plate of roasted broccoli, that is a pattern worth showing a pharmacist, not a verdict.

Meal size is the second variable: a stomach that empties slowly has less room, and people commonly describe a heavy meal sitting for hours before the belching starts, so portion goes in the log alongside content. Carbonation is the third. A fizzy drink adds gas that has to leave somehow, and on a slowly emptying stomach it tends to leave upward; eating quickly and swallowing air does the same. The site's guide to foods that commonly feel uncomfortable on a GLP-1 covers the wider picture of greasy, sugary and oversized meals; this page stays on the sulfur question.

None of this is a diet plan. Whether any food should change in your case is a conversation with your prescriber or a registered dietitian, who can weigh the burping against protein needs, blood sugar and everything else a web page cannot see.

Belching is unpleasant and, by the label's own accounting, common. The harder job is telling it apart from the reactions the same labels put in their warnings sections, because early on they can arrive together.

The Wegovy label's section 5.6, Severe Gastrointestinal Adverse Reactions, reports severe gastrointestinal reactions in 4.1% of injection-treated adults against 0.9% on placebo, and states that Wegovy is not recommended in patients with severe gastroparesis. The Zepbound and Mounjaro labels carry the same gastroparesis statement. Section 5.2 on acute pancreatitis asks clinicians to watch for "persistent or severe abdominal pain (sometimes radiating to the back)," with or without nausea and vomiting. Section 5.3 covers acute gallbladder disease. The post-marketing section lists ileus, intestinal obstruction and severe constipation including fecal impaction as reports received since approval, at frequencies the label says it cannot reliably estimate. The acute kidney injury section ties that risk to dehydration from nausea, vomiting or diarrhea.

Read as a checklist, the following are not burping and should not wait for a pattern to emerge: abdominal pain that is severe, persistent or radiating to the back; repeated vomiting; being unable to keep fluids down; a belly that is swollen and painful rather than merely gassy; days without a bowel movement alongside pain or vomiting. Those are calls to the prescriber the same day, or to emergency services if severe. The Wegovy label also instructs patients to tell any clinician about the medication before a planned surgery or procedure involving anesthesia, because of the emptying delay.

A rotten-egg belch on its own is the thing this page is about. Even then, if it is new, frequent enough to affect meals or sleep, or arrives with heartburn that did not exist before, raise it at the next appointment; a pharmacist can usually take the call sooner.

A single sulfur burp tells you nothing. Two weeks of dated episodes next to what you ate and where you were in the dose cycle can tell a pharmacist quite a lot, at about ten seconds per entry.

Record four things per episode: the time, an intensity on a scale you keep fixed (one to three is enough), the last meal with a rough portion, and which day of the dose cycle it was, day one being dose day. If the label is right that the emptying delay is largest after a dose and fades, episodes should thin out towards the end of the week; if they do not, that is a useful observation in its own right. Note carbonated drinks and anything from the sulfur list separately, because those are the variables a pharmacist will ask about first.

In GLP-1 Tracker each dose entry keeps the date, the injection site and your note in one place, and meals are logged separately, so an episode can be written against that week's injection and read next to what was eaten. The walkthrough on how to log a meal on a GLP-1 covers matching the entry to the plate, logging unfinished meals, and backdating rather than skipping; the procedure in how to keep a GLP-1 symptom journal applies unchanged to the burps. Everything is kept on your device and in your private iCloud, there is no account, and the app draws no conclusions from any of it.

After a fortnight, sort the episodes three ways: by days since dose, by meal, and by the sulfur and carbonation flags. A cluster in the two days after the injection matches the label's description of the emptying delay. A cluster after particular meals is a dietary pattern. No cluster at all is also information, because it argues against the simplest explanations.

What the log cannot do is decide anything. It cannot say whether the burping will fade, whether a food should go, or whether a dose change your prescriber is considering will help. The labels say the emptying delay diminishes over time and that gastrointestinal reactions concentrate during escalation, which is grounds for patience, not for adjusting anything yourself. Your prescriber sets the dose and schedule; your pharmacist can talk through timing and meals. The guide on preparing a summary for your doctor turns the notes into a page they can read in two minutes.

One last distinction. Nausea has its own page on this site. Sulfur burps are a different complaint with a different explanation, and they can be present without any nausea at all, so keep them as their own line in the log rather than folding them into a general stomach entry.