Sulfur Burps on Mounjaro and Other GLP-1s: Why They Happen and When They Matter

Burping that smells like rotten eggs is one of the more unusual gastrointestinal complaints described by some people taking GLP-1-based medications. Online, it is usually called “sulfur burps.”

The term is useful conversationally, but it is important to separate what patients report from what clinical trials have actually measured.

“Sulfur burps” are not a formal adverse-event category used in major GLP-1 clinical trials or prescribing information. Drug labels instead use the medical term eructation, meaning belching. Belching is a documented adverse effect of both tirzepatide and semaglutide, while dyspepsia, abdominal distension, reflux, nausea, vomiting and constipation are also recognized gastrointestinal effects.

The distinctive sulfur-like odor is commonly associated with volatile sulfur compounds such as hydrogen sulfide. However, research has not established that GLP-1 medications directly increase hydrogen sulfide production or identified a single mechanism responsible for “sulfur burps.”

The most scientifically reasonable explanation is therefore more nuanced: GLP-1 therapies alter gastrointestinal motility and gastric emptying, which may create conditions in which belching, reflux and altered gas production become more noticeable in susceptible individuals.

Understanding that distinction matters because sulfur burps are usually a symptom to observe in context, not a diagnosis on their own.

Key Points

• Belching, medically called eructation, is a recognized adverse effect of tirzepatide and semaglutide.
• Tirzepatide and GLP-1 receptor agonists can slow gastric emptying.
• Slower gastric transit may contribute to fullness, dyspepsia, reflux, bloating and belching.
• The rotten-egg smell associated with “sulfur burps” is thought to involve sulfur-containing gases such as hydrogen sulfide, but this mechanism has not been specifically demonstrated in GLP-1 users.
• Gastrointestinal symptoms may become more noticeable during treatment initiation or dose escalation.
• Persistent or severe burping should be interpreted alongside vomiting, abdominal pain, bowel changes, food intake and hydration.
• Severe abdominal pain, repeated vomiting or inability to maintain hydration should not simply be dismissed as a routine GLP-1 side effect.

What Exactly Are Sulfur Burps?

Belching is the release of gas from the stomach or esophagus through the mouth.

The smell associated with a belch depends partly on the gases present in the gastrointestinal tract. Hydrogen sulfide is one of several sulfur-containing compounds produced within the gastrointestinal system and by intestinal microorganisms. It has the characteristic odor commonly associated with rotten eggs.

Research into intestinal sulfur metabolism shows that hydrogen sulfide can be produced through both human cellular metabolism and microbial activity. Gut microorganisms can generate hydrogen sulfide from sulfur-containing substrates, including sulfur-containing amino acids.

That does not, however, mean that every rotten-egg-smelling burp is caused by excessive hydrogen sulfide production in the stomach.

Much of the scientific research on microbial hydrogen sulfide production concerns the lower gastrointestinal tract and colon, whereas a gastric belch originates higher in the digestive system. The biology behind a particular person’s sulfur-smelling burps may therefore involve several interacting factors rather than a simple “too much sulfur” explanation.

This is one reason broad claims that sulfur burps are caused simply by eating too many eggs, protein foods or sulfur-rich vegetables should be treated cautiously.

Are Burps Actually a Recognized Side Effect of Mounjaro?

Yes. Belching is documented in clinical data for tirzepatide.

In the current U.S. prescribing information for Mounjaro (tirzepatide), eructation occurred more frequently in adults receiving tirzepatide than placebo.

Eructation was reported in approximately:

• 0.4% of participants receiving placebo
• 3.0% receiving Mounjaro 5 mg
• 2.5% receiving Mounjaro 10 mg
• 3.3% receiving Mounjaro 15 mg

The prescribing information also documents gastrointestinal effects including nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, abdominal pain, flatulence, reflux and abdominal distension.

Across pooled placebo-controlled trials, gastrointestinal adverse reactions occurred substantially more often in people receiving Mounjaro than in those receiving placebo.

Many reports of nausea, vomiting and diarrhea occurred during dose escalation and decreased over time.

Zepbound contains the same active ingredient, tirzepatide, but is approved for different indications. Its clinical program also documented increased eructation.

Eructation was reported in approximately 1% of participants receiving placebo compared with 4% to 5% of participants receiving Zepbound, depending on dose.

This provides strong evidence that increased belching can occur during tirzepatide therapy.

It does not prove that every case of sulfur-smelling belching is directly caused by tirzepatide.

What About Wegovy and Semaglutide?

Belching is not unique to tirzepatide.

In adult weight-management trials included in the prescribing information for Wegovy (semaglutide), eructation was reported in approximately 7% of participants receiving Wegovy compared with less than 1% receiving placebo.

Dyspepsia, abdominal distension, flatulence and gastroesophageal reflux disease were also reported more frequently with semaglutide.

Pharmacovigilance research examining gastrointestinal adverse events associated with semaglutide has also identified eructation as a reported safety signal.

These findings suggest that belching is better understood as part of the broader gastrointestinal effects of incretin-based therapy, rather than something unique to Mounjaro or tirzepatide.

Importantly, percentages from different clinical trials should not be used to conclude that one medication is more likely to cause belching than another. Trial populations, doses, study designs and methods of recording adverse events differ.

Why Might GLP-1 Medications Cause More Burping?

There is unlikely to be one universal mechanism.

Several physiological effects may overlap.

1. Slower Gastric Emptying

One of the best-established explanations involves gastric motility.

Tirzepatide delays gastric emptying, with the effect generally being greatest after initial exposure and diminishing to some degree with repeated administration. GLP-1 receptor agonists such as semaglutide can also delay gastric emptying.

This is part of the pharmacology of these medications.

When gastric contents remain in the stomach for longer, some people may experience:

• prolonged fullness
• early satiety
• nausea
• abdominal distension
• dyspepsia
• reflux
• belching

Research examining people taking GLP-1 therapies has also found increased residual gastric contents in some patients compared with people not taking these medications, although the clinical significance varies.

Slower gastric emptying therefore provides a biologically plausible explanation for why belching could become more noticeable.

It still does not establish exactly why a particular belch develops a sulfur-like odor.

2. Changes in Digestion and Gastrointestinal Transit

When gastrointestinal transit changes, the timing and location of food breakdown can also change.

Food interacts with:

• stomach acid
• digestive enzymes
• intestinal bacteria
• carbohydrates
• proteins
• sulfur-containing amino acids

Gut microorganisms are capable of producing hydrogen sulfide and other gases during metabolism.

Research on the intestinal microbiome has shown that sulfur metabolism is influenced by both dietary substrates and bacterial pathways. Dietary protein can provide sulfur-containing amino acids such as cysteine and methionine, although the relationship between diet and hydrogen sulfide production is complex.

A reasonable hypothesis is that altered gastrointestinal transit may change how these processes are experienced by some GLP-1 users.

But this remains a hypothesis, rather than proof that delayed gastric emptying directly causes sulfur burps through fermentation.

That distinction is important in a topic where anecdotal explanations frequently become presented as established medical facts.

3. Dyspepsia, Reflux and Abdominal Distension Can Occur Together

Belching rarely needs to be considered in isolation.

GLP-1 clinical trials also document gastrointestinal effects such as:

• dyspepsia
• gastroesophageal reflux
• abdominal distension
• flatulence
• nausea
• constipation

Belching commonly overlaps with reflux and other gastrointestinal symptoms even outside GLP-1 therapy.

Someone experiencing sulfur burps may therefore actually be experiencing a broader gastrointestinal pattern involving fullness, reflux, constipation or altered digestion.

The surrounding symptoms often provide more clinically useful information than the smell of the burp itself.

Why Can Sulfur Burps Appear After Increasing a GLP-1 Dose?

Gastrointestinal adverse effects commonly become more noticeable during dose escalation.

Both semaglutide and tirzepatide are normally introduced using gradual dose-escalation schedules partly to improve gastrointestinal tolerability.

Clinical analyses of both therapies show that gastrointestinal adverse effects frequently occur during or shortly after dose escalation and often become less frequent with continued treatment.

Therefore, if sulfur burps suddenly appear after an increase in dose, the timing may be relevant.

It does not automatically mean the new dose is inappropriate.

But recurrent gastrointestinal symptoms following each dose increase are useful information to discuss with the healthcare professional supervising treatment.

Do not change, delay or reduce a prescribed GLP-1 dose based only on gastrointestinal symptoms without discussing the situation with your prescriber.

Do Sulfur Burps Mean You Have Gastroparesis?

No.

This is an important distinction.

GLP-1 medications can delay gastric emptying as a pharmacological effect. That is not equivalent to diagnosing gastroparesis.

Gastroparesis is a clinical disorder involving delayed stomach emptying in the absence of a mechanical obstruction, accompanied by relevant symptoms and usually requiring medical assessment.

Burping alone does not establish gastroparesis.

A clinician may become more concerned about significant gastric dysfunction when belching occurs alongside symptoms such as:

• recurrent or persistent vomiting
• pronounced early satiety
• prolonged fullness after very small meals
• persistent nausea
• significant abdominal distension
• difficulty maintaining adequate food or fluid intake

Current Mounjaro and Zepbound prescribing information states that these medications are not recommended for people with severe gastroparesis.

Persistent symptoms therefore deserve evaluation rather than self-diagnosis.

What Can You Do About Sulfur Burps While Taking a GLP-1?

There is no established clinical guideline specifically for “GLP-1 sulfur burps.”

Management should therefore focus on improving overall gastrointestinal tolerability and identifying patterns.

Eat Smaller Meals

Large meals may be more difficult to tolerate when gastric emptying is slowed.

Expert recommendations for managing gastrointestinal effects during GLP-1 therapy commonly emphasize smaller meal portions and stopping eating when comfortably full rather than continuing beyond satiety.

This may be particularly relevant if burping repeatedly occurs after large meals.

Be Cautious With Very High-Fat Meals

High-fat meals can already take longer to digest and may worsen nausea, fullness or dyspeptic symptoms in some people receiving GLP-1 therapy.

Clinical guidance for gastrointestinal tolerability commonly recommends temporarily limiting particularly fatty meals when gastrointestinal symptoms are prominent.

That does not mean dietary fat needs to be eliminated.

The objective is symptom management, not unnecessary dietary restriction.

Maintain Adequate Hydration

Vomiting, diarrhea, reduced appetite and lower overall food intake can all contribute to inadequate hydration.

Fluid intake becomes especially important if sulfur burps are occurring alongside other gastrointestinal symptoms.

Tracking water intake alongside symptoms and injection timing may help determine whether an uncomfortable gastrointestinal period is also associated with reduced fluid intake.

Pay Attention to Eating Speed

People taking GLP-1 medications may reach fullness sooner than they expect.

Eating quickly can make it easier to consume more food before satiety signals become apparent.

Slowing down, eating smaller portions and stopping when comfortably full may improve gastrointestinal tolerance for some users.

Should You Avoid Eggs, Protein or Other Sulfur-Rich Foods?

Not automatically.

This is where many explanations of sulfur burps become overly simplistic.

Eggs, meat, dairy products, cruciferous vegetables and many other foods contain sulfur-containing compounds or amino acids. Dietary protein can influence intestinal hydrogen sulfide metabolism.

However, there is no good clinical evidence showing that people using GLP-1 medications who experience sulfur burps should routinely eliminate sulfur-rich foods.

This distinction is particularly important for protein.

People losing substantial amounts of weight during GLP-1 therapy still need adequate nutrition, and preservation of lean mass is an important consideration during weight loss.

Unnecessarily removing major protein sources because they contain sulfur could create a different nutritional problem.

A more useful strategy is individualized observation.

If the same food or type of meal repeatedly precedes symptoms, that pattern may be worth discussing with a healthcare professional or registered dietitian.

One episode after eating eggs does not establish that eggs caused the symptom.

What Should You Track When Sulfur Burps Keep Happening?

A single symptom entry provides limited information.

Repeated observations can reveal patterns.

Medication and Dose

Record which medication and dose you were taking when symptoms occurred.

This becomes particularly relevant following a recent dose increase.

Time Since Your Last Injection

Consider whether symptoms begin:

• on injection day
• the following day
• 24 to 48 hours later
• midway through the treatment week
• shortly before the next scheduled dose

A symptom that repeatedly occurs at approximately the same point after each injection provides more useful information than an isolated episode.

Symptom Severity

Record whether the burping is:

• mild
• moderate
• severe
• interfering with eating
• interfering with sleep or normal activities

Severity matters when deciding whether a symptom can simply be observed or should be discussed with a healthcare professional.

Associated Symptoms

Burping accompanied by mild fullness is very different from burping accompanied by repeated vomiting or severe abdominal pain.

Consider whether you also experience:

• nausea
• vomiting
• reflux
• abdominal pain
• bloating
• diarrhea
• constipation
• loss of appetite

Tracking symptoms together can provide considerably more context.

Food Patterns

Instead of immediately eliminating individual foods, look for repetition.

Consider whether symptoms repeatedly follow:

• unusually large meals
• very fatty meals
• a particular food
• late-night meals
• periods of unusually low food intake
• eating considerably faster than usual

Repeated patterns are generally more informative than isolated associations.

Hydration

Record your water intake, particularly if nausea or appetite suppression has reduced normal drinking.

Vomiting or diarrhea makes hydration even more important.

Bowel Changes

Constipation and broader changes in gastrointestinal transit may be relevant when interpreting bloating and gas symptoms.

If sulfur burps repeatedly occur alongside constipation or other bowel changes, recording both may provide more useful information for your healthcare professional.

Look for Patterns Across Several Weeks

Peptimize is designed around longitudinal tracking rather than trying to interpret one isolated data point.

The purpose is not to prove why the symptom happened.

Instead, tracking can help answer more useful questions:

• Does it appear after every injection?
• Did it begin only after dose escalation?
• Does it occur with nausea?
• Does constipation appear at the same time?
• Are you eating less or drinking less during these periods?
• Is the symptom becoming progressively more severe?

A structured history can be much easier to discuss at a medical appointment than trying to remember several weeks of symptoms from memory.

When Are Sulfur Burps More Than an Annoying Side Effect?

Sulfur burps by themselves are usually less informative than the symptoms occurring with them.

Certain accompanying symptoms deserve more attention.

Contact a Healthcare Professional If Symptoms Are Persistent or Worsening

Medical assessment may be appropriate when belching:

• becomes frequent or progressively worse
• repeatedly interferes with eating
• persists despite being on a stable dose
• appears alongside substantial reflux
• occurs with persistent nausea
• is associated with ongoing diarrhea or constipation
• consistently appears following dose escalation and does not settle

Other gastrointestinal disorders, dietary factors, medications and infections can also cause belching or gastrointestinal symptoms.

Not everything that occurs while taking a GLP-1 medication is necessarily caused by that medication.

Seek Prompt Medical Attention for Severe Symptoms

Do not assume every gastrointestinal symptom is simply part of GLP-1 treatment.

Seek prompt medical assessment for symptoms such as the following.

Severe or Persistent Abdominal Pain

GLP-1 prescribing information advises monitoring for symptoms consistent with acute pancreatitis, including persistent severe abdominal pain that may radiate to the back and may or may not occur with vomiting.

Severe abdominal pain should not be dismissed as ordinary indigestion.

Repeated Vomiting or Inability to Keep Fluids Down

Persistent vomiting can lead to dehydration and volume depletion.

If you cannot maintain adequate hydration, medical assessment may be necessary.

Marked Abdominal Swelling With Severe Pain

Severe or unusual abdominal symptoms should not be managed only through food changes or symptom tracking.

Signs of Significant Dehydration

Possible signs include:

• very low urine output
• pronounced dizziness
• weakness
• inability to maintain adequate fluid intake

Fever, Bloody Stool or Severe Diarrhea

These features may suggest another gastrointestinal condition and should not automatically be attributed to a GLP-1 medication.

Symptom tracking is useful for routine patterns. It is not a substitute for medical evaluation when warning signs appear.

Are Sulfur Burps a Sign That Mounjaro Is Working?

No.

Side effects are not a reliable measure of treatment effectiveness.

Someone can respond to tirzepatide or semaglutide without experiencing sulfur burps, nausea or other noticeable gastrointestinal effects.

Similarly, experiencing stronger gastrointestinal symptoms does not mean a medication is producing a better therapeutic response.

Clinical research with tirzepatide has demonstrated meaningful weight reduction even among participants who did not experience common gastrointestinal adverse events.

Treatment effectiveness and treatment tolerability are related questions, but they are not the same question.

Frequently Asked Questions

Are Sulfur Burps Common With Mounjaro?

Clinical trials did not specifically measure “sulfur burps,” but they did measure eructation or belching.

In Mounjaro prescribing information, eructation occurred in approximately 2.5% to 3.3% of adults receiving tirzepatide, depending on dose, compared with approximately 0.4% receiving placebo.

The actual frequency of specifically sulfur-smelling burps is unknown.

Can Zepbound Cause Sulfur Burps?

Zepbound contains tirzepatide, the same active ingredient found in Mounjaro.

Eructation was reported in approximately 4% to 5% of participants receiving Zepbound compared with approximately 1% receiving placebo.

Clinical trials did not separately classify sulfur-smelling burps.

Can Ozempic or Wegovy Cause Sulfur Burps?

Semaglutide can cause gastrointestinal adverse effects including belching.

In adult Wegovy weight-management trials, eructation was reported in approximately 7% of participants receiving semaglutide compared with less than 1% receiving placebo.

Again, specifically sulfur-smelling burps were not separately studied.

Why Do Sulfur Burps Happen After My Injection?

The exact reason cannot be determined from timing alone.

GLP-1-based therapies affect gastrointestinal motility, and gastrointestinal adverse effects can become more noticeable during treatment initiation or following dose escalation.

If the symptom repeatedly appears at a similar interval after each dose, recording that pattern may provide useful information for your healthcare professional.

Why Do My Sulfur Burps Become Worse After Increasing My Mounjaro Dose?

Gastrointestinal adverse effects frequently become more noticeable during dose escalation.

If the symptom began or became substantially worse after increasing tirzepatide or semaglutide, that timing may be clinically relevant.

Do not change your prescribed dose without discussing it with your healthcare professional.

Do Sulfur Burps Mean Food Is Sitting in My Stomach?

Not necessarily.

GLP-1 medications can slow gastric emptying, but a sulfur-smelling burp cannot tell you how quickly your stomach is emptying.

It also cannot diagnose gastroparesis.

Should I Stop Mounjaro Because of Sulfur Burps?

Do not change or discontinue prescribed treatment based solely on information in an educational article.

Mild gastrointestinal symptoms and severe or persistent gastrointestinal symptoms require very different responses.

Discuss recurrent or troublesome symptoms with the healthcare professional managing your treatment, and seek prompt medical attention when warning signs are present.

The Bottom Line

Sulfur burps are a real experience reported by some people taking Mounjaro, Zepbound, Wegovy and other GLP-1-based therapies, but the science is more precise than the name suggests.

Clinical evidence clearly shows that belching is an adverse effect associated with tirzepatide and semaglutide.

These medications can also affect gastric emptying and are associated with dyspepsia, reflux, nausea, bloating and other gastrointestinal symptoms.

What clinical research has not established is a specific pathway in which GLP-1 medication directly produces hydrogen sulfide and therefore causes the characteristic rotten-egg smell.

For most people, the most useful approach is therefore not to focus on the odor alone.

Instead, look at the broader pattern.

When did it begin?

Did your dose recently change?

Does it recur at approximately the same point after every injection?

Does it appear with nausea, reflux, constipation or bloating?

Were you eating differently?

Were you adequately hydrated?

Longitudinal tracking can turn an isolated and unpleasant symptom into a more useful record.

And when sulfur burps occur alongside severe abdominal pain, persistent vomiting, significant dehydration or other concerning gastrointestinal symptoms, the priority should shift from tracking the pattern to seeking appropriate medical care.

References

1. Eli Lilly and Company. Mounjaro (tirzepatide) U.S. Prescribing Information. Revised 2026.
2. Eli Lilly and Company. Zepbound (tirzepatide) U.S. Prescribing Information. Revised 2026.
3. Novo Nordisk. Wegovy (semaglutide) U.S. Prescribing Information. Revised 2026.
4. Shu Y, et al. Gastrointestinal adverse events associated with semaglutide: A pharmacovigilance study based on the FDA Adverse Event Reporting System. Frontiers in Public Health. 2022.
5. Chang MG, Ripoll JG, Lopez E, et al. A Scoping Review of GLP-1 Receptor Agonists: Are They Associated with Increased Gastric Contents, Regurgitation, and Aspiration Events? Journal of Clinical Medicine. 2024;13:6336.
6. Blachier F, Beaumont M, Kim E. Cysteine-derived hydrogen sulfide and gut health: a matter of endogenous or bacterial origin. Current Opinion in Clinical Nutrition and Metabolic Care. 2019;22(1):68-75.
7. Impact of diet on hydrogen sulfide production: implications for gut health. Current Opinion in Clinical Nutrition and Metabolic Care. Review of dietary protein, fiber and intestinal hydrogen sulfide metabolism.
8. Gastrointestinal tolerability and weight reduction associated with tirzepatide in adults with obesity or overweight with and without type 2 diabetes in the SURMOUNT-1 to SURMOUNT-4 trials. Clinical analysis of gastrointestinal tolerability during tirzepatide therapy.
9. Wharton S, Davies M, Dicker D, et al. Managing the gastrointestinal side effects of GLP-1 receptor agonists in obesity: recommendations for clinical practice. Postgraduate Medicine. 2022;134(1):14-19.
10. Gorgojo-Martínez JJ, Mezquita-Raya P, Carretero-Gómez J, et al. Clinical Recommendations to Manage Gastrointestinal Adverse Events in Patients Treated with GLP-1 Receptor Agonists: A Multidisciplinary Expert Consensus. Journal of Clinical Medicine. 2023;12(1):145.

Medical Disclaimer

This article is for educational purposes only and does not provide medical advice, diagnosis or treatment. Peptimize is a personal tracking tool and does not recommend medications, doses or treatment changes. Always follow the instructions provided by your healthcare professional and the approved prescribing information for your medication. Seek appropriate medical care for severe, persistent or concerning symptoms.