"Sulfur burps" is a patients' phrase, not a label term. No current US GLP-1 label contains the word sulfur. What the labels do record is eructation — belching — and on several of them it is the side effect with the widest gap between drug and placebo in relative terms: 7% of people on Wegovy in its weight trials against fewer than 1% on placebo. The smell is a different matter. No study indexed in PubMed has tested whether these drugs make burps smell of sulfur, or why they would.
This page sets out what the labels record, how often, and where the evidence stops. The labels were read on 11 October 2026 from DailyMed, using the manufacturers' own versions. It reports what the documents say; it does not advise on treatment.
What the labels call it
The adverse-reaction tables use standard medical terms, and the patient Medication Guides translate them:
| Label term | What it means | Medication Guide wording |
|---|---|---|
| Eructation | Belching | "belching" |
| Dyspepsia | Indigestion, upper-stomach discomfort | "indigestion" or "upset stomach" |
| Gastroesophageal reflux disease | Acid coming back up | "heartburn" |
| Flatulence | Gas | "gas" |
| Abdominal distension | A swollen or bloated stomach | "feeling bloated" |
A sulfur burp, as patients describe it, would be counted under eructation — and perhaps dyspepsia — with no record of the smell.
Belching and indigestion in every current label
The ratio column is glp1ledger's arithmetic — the drug rate divided by the placebo rate for eructation — which no label prints. Where a label reports a rate below its table's cut-off, the figure is from the text under the table.
| Label (effective date) | Population | Eructation: placebo → drug | Ratio | Dyspepsia: placebo → drug |
|---|---|---|---|---|
| Wegovy injection (2026-06-18) | Adults, weight | under 1% → 7% (2.4 mg) | over 7× | 3% → 9% |
| Wegovy injection, adolescents | Ages 12+, weight | 0% → 4% | — | not listed |
| Zepbound (2026-08-28) | Adults, weight | 1% → 4%, 5%, 5% (5/10/15 mg) | 4–5× | 4% → 9%, 9%, 10% |
| Saxenda (2026-02-25) | Adults, weight | 0.2% → 4.5% (3 mg) | 22× | 2.7% → 9.6% |
| Foundayo tablets (2026-07-29) | Adults, weight | 1% → 6%, 8%, 8% (5.5/9/17.2 mg) | 6–8× | 4% → 12%, 16%, 13% |
| Mounjaro (2026-08-27) | Adults, type 2 diabetes | 0.4% → 3.0%, 2.5%, 3.3% (5/10/15 mg) | 6–8× | 3% → 8%, 8%, 5% |
| Ozempic injection (2026-06-01) | Adults, type 2 diabetes | 0% → 2.7% (0.5 mg), 1.1% (1 mg) | — | 1.9% → 3.5%, 2.7% |
| Semaglutide tablets, Rybelsus/Ozempic (2026-01-30) | Adults, type 2 diabetes | 0% → 0.6% (7 mg), 2% (14 mg) | — | 0.6% → 3% (7 mg), 0.6% (14 mg) |
| Trulicity (2026-06-16) | Adults, type 2 diabetes | 0.2% → 0.6% (0.75 mg), 1.6% (1.5 mg) | 3–8× | 2.3% → 4.1%, 5.8% |
| Victoza (2025-10-14) | Adults, type 2 diabetes | not listed | — | 1% → 4%, 7% |
Three things follow from the table:
- Belching is uncommon in absolute terms but rare without the drug. On every label that prints it, the placebo rate is 1% or less. That is why the ratios are high while the counts stay small: on Saxenda, 4.5% against 0.2%.
- The weight-loss doses record more belching than the diabetes doses. The four weight-management labels print 4% to 8%; the diabetes labels 0.6% to 3.3%.
- Indigestion is the larger figure. Dyspepsia runs at 9% to 16% on the weight-loss labels, two to four times placebo. Whether a "sulfur burp" is recorded as one, the other or both depends on how a trial investigator coded the complaint.
The signal in routine-use reports
Trial tables count everything reported, including events that happen anyway. Pharmacovigilance studies look the other way: they ask which events are reported for a drug disproportionately often compared with every other drug in the FDA's database. In a 2022 analysis of the FDA Adverse Event Reporting System from 2018 to 2022, covering 5,442 gastrointestinal cases for semaglutide, researchers detected 45 signals. Eructation was the strongest of them, with a lower 95% confidence bound of the reporting odds ratio of 42.03 — at the top of a range that started at 1.01 (Shu et al., 2022).
A reporting odds ratio is not a rate and cannot say how many people are affected, and voluntary reports can be shaped by publicity. What it does say is that belching is reported for semaglutide far out of proportion to its background frequency — the same picture as the label ratios.
The sulfur explanation, and the absence of evidence for it
The explanation that circulates online is that food stays longer in the stomach, ferments, and produces hydrogen sulfide — the gas that smells of rotten eggs. Half of that is documented: every label read for this page states that the drug delays gastric emptying, which is why the labels also warn about absorption of other oral medicines and about anaesthesia. The other half is not:
- A PubMed search run on 11 October 2026 for GLP-1 drug terms with "hydrogen sulfide" or "sulfur burps" returned 13 records. They concern hydrogen sulfide as a signalling molecule in heart and blood-vessel research, or the reverse question: whether hydrogen sulfide made by gut bacteria changes the body's own GLP-1 (a 2024 mouse study in Nature Metabolism reported that it lowers GLP-1 levels). None measures gas or breath in people taking a GLP-1 drug.
- A search for "sulfur burps" in any context returned 3 records, none about these medicines.
- A search for GLP-1 drug terms with eructation, belching or burping returned 15 records — pharmacovigilance studies, oral-health reviews, a meta-analysis and small clinical reports. None of their abstracts mentions smell, odour or sulfur.
So the honest position is that sulfur-smelling burps are a widely reported experience that the research record has not yet examined. The delay in stomach emptying is established; the link from it to a sulfur smell is a plausible hypothesis that no indexed study has tested.
What the labels say about timing
No label reports how long belching lasts. The Zepbound and Mounjaro labels state that most nausea, vomiting and diarrhoea occurred during dose escalation and decreased over time, but they do not give that pattern for eructation. The episode lengths that do exist — for nausea, diarrhoea, vomiting and constipation — are on the episode-length comparison, and nausea, the most common upper-stomach effect, has its own page.
What this page cannot tell you
- Rates count anyone who reported belching at least once, of any severity; they do not measure how often it happened to each person.
- Ratios built on placebo rates below 1% are unstable: a difference of a handful of people in the placebo arm changes them a great deal.
- No trial recorded the smell, so no figure on this page is a rate of sulfur burps.
- No trial compared two GLP-1 drugs for belching in any table a label reports, so the table ranks nothing.
Belching that persists, or comes with vomiting, severe pain or difficulty swallowing, is a matter for a prescriber. Every other side effect in the class is set out on GLP-1 side effects, with the brand pages for Zepbound and Ozempic.
Sources
- Prescribing information and Medication Guides read on DailyMed, 2026-10-11 (manufacturer label versions, effective dates as shown): WEGOVY (Novo Nordisk, set ID ee06186f-2aa3-4990-a760-757579d8f77b); ZEPBOUND (Eli Lilly, 487cd7e7-434c-4925-99fa-aa80b1cc776b), Table 1 and sections 5.9, 7.2; SAXENDA (Novo Nordisk, 3946d389-0926-4f77-a708-0acb8153b143), Table 2; FOUNDAYO (Eli Lilly, 8ac446c5-feba-474f-a103-23facb9b5c62), Table 1; MOUNJARO (Eli Lilly, d2d7da5d-ad07-4228-955f-cf7e355c8cc0), Table 1 and section 6.1; OZEMPIC injection (Novo Nordisk, adec4fd2-6858-4c99-91d4-531f5f2a2d79), section 6.1 and 7.2; semaglutide tablets, OZEMPIC/RYBELSUS (Novo Nordisk, 27f15fac-7d98-4114-a2ec-92494a91da98), section 6.1; TRULICITY (Eli Lilly, 463050bd-2b1c-40f5-b3c3-0a04bb433309), section 6.1; VICTOZA (Novo Nordisk, 5a9ef4ea-c76a-4d34-a604-27c5b505f5a4), Table 1. All at dailymed.nlm.nih.gov.
- Shu Y, He X, Wu P, et al., "Gastrointestinal adverse events associated with semaglutide: A pharmacovigilance study based on FDA adverse event reporting system", Frontiers in Public Health 2022;10:996179, PMC9631444.
- Qi Q, et al., "Hydrogen sulfide produced by the gut microbiota impairs host metabolism via reducing GLP-1 levels in male mice", Nature Metabolism 2024, doi:10.1038/s42255-024-01068-x (PubMed 39030389).
- PubMed searches run 2026-10-11 through NCBI E-utilities:
(semaglutide OR tirzepatide OR "GLP-1") AND ("sulfur burps" OR "sulphur burps" OR "hydrogen sulfide" OR "hydrogen sulphide")(13 records);"sulfur burps" OR "sulphur burps" OR "sulfur burping"(3);(semaglutide OR tirzepatide OR liraglutide OR dulaglutide OR "GLP-1 receptor agonist") AND (eructation OR belching OR burping)(15).