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Sulphur burps—belching with a distinctive rotten egg odour—are an increasingly recognised side effect amongst patients taking GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and liraglutide (Saxenda, Victoza). These medicines, prescribed for type 2 diabetes and weight management, slow gastric emptying to regulate blood glucose and promote satiety. However, this delayed digestion can lead to increased bacterial fermentation of sulphur-containing proteins, producing hydrogen sulphide gas. Whilst often manageable through dietary adjustments and eating habit modifications, understanding the underlying mechanism helps patients navigate this uncomfortable side effect whilst continuing beneficial treatment. This article explores why GLP-1 medicines cause sulphur burps and provides evidence-based strategies for effective management.
Quick Answer: Sulphur burps during GLP-1 therapy occur because these medicines slow gastric emptying, allowing increased bacterial fermentation of sulphur-containing proteins in the digestive tract, which produces hydrogen sulphide gas.
Sulphur burps are characterised by an unpleasant odour resembling rotten eggs when belching. This distinctive smell results from hydrogen sulphide gas, a byproduct of bacterial breakdown of sulphur-containing proteins in the digestive tract. Whilst occasional sulphur burps are generally harmless, their frequency and intensity can increase under certain circumstances, causing considerable discomfort and social embarrassment.
The production of hydrogen sulphide occurs primarily when gut bacteria ferment proteins containing sulphur-based amino acids such as cysteine and methionine. These amino acids are found in various foods including eggs, meat, poultry, dairy products, and certain vegetables like broccoli and Brussels sprouts. This fermentation process mainly occurs in the small intestine and colon, though it can be influenced by how long food remains in the upper digestive tract.
Several factors can contribute to sulphur burps beyond dietary choices. Delayed gastric emptying (gastroparesis) is a possible mechanism, as food sitting longer in the stomach provides more opportunity for bacterial activity downstream in the digestive process. Other contributing factors include:
Small intestinal bacterial overgrowth (SIBO)
Gastrointestinal infections or parasites
Certain medicines that slow digestion (e.g., opioids, anticholinergics, tricyclic antidepressants, GLP-1 receptor agonists)
Food intolerances or malabsorption disorders
Swallowing excess air (aerophagia)
Consumption of carbonated beverages
Understanding the underlying cause is essential for effective management. When sulphur burps occur alongside other symptoms such as abdominal pain, diarrhoea, or persistent nausea, they may indicate an underlying digestive condition requiring medical evaluation. The connection between sulphur burps and GLP-1 medicines relates specifically to how these drugs affect the rate of gastric emptying, which we shall explore in the following section.
Glucagon-like peptide-1 (GLP-1) receptor agonists, including semaglutide (Ozempic, Wegovy), dulaglutide (Trulicity), and liraglutide (Victoza, Saxenda), are increasingly prescribed for type 2 diabetes management and weight loss. These medicines work by mimicking the action of naturally occurring GLP-1, an incretin hormone released by the intestines in response to food intake. Understanding their mechanism of action helps explain why digestive side effects, including sulphur burps, commonly occur.
The primary mechanisms through which GLP-1 medicines affect digestion include:
Delayed gastric emptying: GLP-1 receptor agonists significantly slow the rate at which food moves from the stomach into the small intestine. This deliberate slowing helps regulate blood glucose levels and promotes satiety, contributing to weight loss. This prolonged retention of food in the stomach may contribute to sulphur-smelling burps in some people.
Altered gut motility: GLP-1 agonists influence the entire gastrointestinal tract, potentially affecting digestive processes.
Clinical trials have documented gastrointestinal adverse effects as the most common side effects of GLP-1 medicines. According to the Summary of Product Characteristics (SmPC), nausea occurs in approximately 20% of patients taking semaglutide (Ozempic), up to 21% with dulaglutide (Trulicity), and 20-40% with liraglutide (Saxenda), depending on dose. Whilst sulphur burps are not always explicitly listed in product literature, they may occur as a consequence of the digestive changes these medicines cause.
The severity of gastrointestinal effects typically correlates with dosage and often diminishes as the body adapts to treatment. Side effects frequently occur during dose escalation and may lessen over time, usually within the first few weeks to months. However, individual responses vary considerably, and some patients experience persistent digestive symptoms requiring management strategies or dose adjustments.
It's worth noting that GLP-1 receptor agonists should be used with caution in people with severe gastrointestinal disease, including severe gastroparesis, as these conditions may be exacerbated by further slowing of gastric emptying.
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Effectively managing sulphur burps whilst continuing GLP-1 therapy requires a multifaceted approach focusing on dietary modifications, eating habits, and lifestyle adjustments. Most patients can significantly reduce symptoms without discontinuing their medicine, which is important given the substantial metabolic benefits these drugs provide.
Dietary modifications form the cornerstone of management:
Reduce sulphur-rich foods: Temporarily limit consumption of eggs, red meat, poultry, dairy products, cruciferous vegetables (broccoli, cauliflower, cabbage), garlic, and onions. Reintroduce these foods gradually to identify personal triggers.
Avoid carbonated beverages: These increase gas in the digestive system and can exacerbate burping.
Choose a balanced diet: Focus on foods that you tolerate well and avoid known personal triggers.
Stay well-hydrated: Adequate water intake supports overall digestive health.
Eating habits and meal timing significantly impact symptom severity:
Consume smaller, more frequent meals rather than large portions, as this reduces the burden on an already-slowed digestive system.
Choose lower-fat meals, especially during dose escalation periods, as fatty foods can worsen GLP-1-related digestive symptoms.
Eat slowly and chew thoroughly to aid digestion and reduce air swallowing.
Avoid lying down immediately after eating; remain upright for at least two hours post-meal.
Consider having your last meal earlier in the evening to allow adequate digestion time before sleep.
Additional management strategies include:
Probiotics: Some patients report improvement with probiotic supplements, though evidence remains limited. Discuss with your GP before starting.
Peppermint tea: May help soothe the digestive tract and reduce gas, though it can worsen reflux in some people. Ginger tea is an alternative if you experience reflux symptoms.
Over-the-counter remedies: Simeticone (such as Wind-eze tablets or capsules) may provide temporary relief by breaking up gas bubbles, though it does not address the underlying cause.
If symptoms persist despite these measures, consult your prescribing clinician about potential dose adjustments or alternative GLP-1 formulations, as individual responses vary between different agents in this class. Your doctor may also review any other medicines you take that could be slowing digestion and contributing to symptoms.
Whilst sulphur burps and mild digestive discomfort are common when initiating GLP-1 therapy, certain symptoms warrant prompt medical evaluation. Distinguishing between expected side effects and potentially serious complications is essential for patient safety.
Contact your GP or prescribing clinician if you experience:
Persistent or worsening symptoms that do not improve after dose escalation has stabilised or are worsening at any time.
Severe or persistent vomiting that prevents adequate fluid or food intake, as this may lead to dehydration and electrolyte imbalances.
Severe abdominal pain, particularly if constant or progressively worsening, which could indicate pancreatitis—a rare but serious adverse effect of GLP-1 medicines.
Signs of dehydration: decreased urination, dark urine, dizziness, or extreme thirst.
Unexplained weight loss beyond expected therapeutic effects, or inability to maintain adequate nutrition.
Sudden pain in the upper right abdomen (may radiate to the shoulder), fever, yellowing of the skin/eyes, pale stools or dark urine—these could indicate gallbladder problems, which can be associated with GLP-1 medicines and rapid weight loss.
Seek immediate medical attention (A&E or call 999) if you develop:
Severe, persistent abdominal pain radiating to the back (potential pancreatitis)
Bloody or black, tarry stools
Persistent vomiting with inability to keep down fluids
Signs of severe dehydration or altered consciousness
Symptoms of bowel obstruction (severe bloating, inability to pass gas or stool, severe cramping)
For urgent but non-life-threatening concerns outside of GP hours, contact NHS 111 for advice.
According to NICE guidance, healthcare professionals should provide clear safety-netting advice when prescribing GLP-1 receptor agonists, including information about expected side effects and warning signs requiring medical review. Regular follow-up appointments are essential, particularly during dose escalation phases.
Important considerations for ongoing management:
Your prescriber may need to adjust your dose, switch to an alternative GLP-1 medicine, or investigate other potential causes of digestive symptoms. Never discontinue prescribed medicine without medical guidance, particularly if you have diabetes, as this could affect glycaemic control. If sulphur burps are accompanied by other concerning symptoms such as unexplained fever, significant changes in bowel habits, or unintentional weight loss beyond therapeutic goals, further investigation may be warranted to rule out concurrent gastrointestinal conditions unrelated to your medicine.
You can report any suspected side effects from medicines to the MHRA through the Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).
Sulphur burps typically occur during dose escalation and often diminish within the first few weeks to months as the body adapts to treatment. However, individual responses vary, and some patients may experience persistent symptoms requiring dietary modifications or dose adjustments.
Whilst prevention may not be complete, you can significantly reduce sulphur burps by limiting sulphur-rich foods (eggs, red meat, cruciferous vegetables), eating smaller frequent meals, avoiding carbonated beverages, and remaining upright for at least two hours after eating.
Never discontinue GLP-1 therapy without medical guidance, particularly if prescribed for diabetes management. Most patients can manage sulphur burps through dietary modifications, but consult your prescribing clinician if symptoms persist or worsen despite these measures.
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DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
