Mounjaro sulfur burps and diarrhoea are amongst the most commonly reported gastrointestinal side effects of tirzepatide, affecting many patients during initial treatment or dose escalation. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. These digestive symptoms occur primarily because the medication slows gastric emptying and alters gut hormone signalling. Whilst often troublesome, these effects typically diminish as the body adjusts to treatment. Understanding why they occur and implementing practical management strategies can significantly improve tolerability and treatment adherence.

Understanding Mounjaro and Common Gastrointestinal Side Effects

Mounjaro (tirzepatide) is a once-weekly injectable medication licensed in the UK for the treatment of type 2 diabetes mellitus and, more recently, for weight management in adults with obesity or overweight with weight-related comorbidities. As a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, Mounjaro works by mimicking naturally occurring incretin hormones that regulate blood glucose levels and appetite.

Whilst Mounjaro has demonstrated significant efficacy in glycaemic control and weight reduction in clinical trials, gastrointestinal side effects are amongst the most commonly reported adverse reactions. According to the Summary of Product Characteristics (SmPC) approved by the Medicines and Healthcare products Regulatory Agency (MHRA), gastrointestinal disturbances affect a substantial proportion of patients, particularly during the initial weeks of treatment or following dose escalation.

The most frequently reported gastrointestinal side effects include:

• Nausea (very common, affecting more than 1 in 10 patients)

• Diarrhoea (very common, affecting more than 1 in 10 patients)

• Vomiting (common to very common, depending on dose)

• Decreased appetite (very common)

• Constipation

• Abdominal pain or discomfort

• Dyspepsia (indigestion)

• Belching, which may occasionally have a sulphurous odour

These symptoms typically occur because GLP-1 receptor agonists slow gastric emptying—the rate at which food leaves the stomach—and alter gastrointestinal motility. Whilst most patients experience mild to moderate symptoms that improve over time as the body adjusts to the medication, some individuals find these effects troublesome enough to affect their quality of life. Understanding why these symptoms occur and how to manage them effectively is essential for treatment adherence and patient wellbeing.

If you experience side effects from any medication, you can report them through the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Why Mounjaro Causes Sulphur Burps and Diarrhoea

The mechanism by which Mounjaro causes gastrointestinal side effects relates primarily to its pharmacological action on the digestive system. GLP-1 receptor agonists significantly delay gastric emptying, meaning food remains in the stomach for longer periods than usual. This delayed gastric emptying is well-established and appears to contribute to many of the gastrointestinal symptoms experienced by patients.

Sulphur burps—characterised by belching with a distinctive rotten egg odour—occur when hydrogen sulphide gas is present in the digestive tract. The delayed gastric emptying caused by Mounjaro may contribute to this symptom. Certain foods high in sulphur compounds (such as eggs, red meat, cruciferous vegetables, and dairy products) can produce hydrogen sulphide during digestion. When combined with increased belching, which is a known side effect of Mounjaro, this can result in the characteristic sulphurous odour.

The exact mechanism of diarrhoea with Mounjaro is not fully established, but likely involves the medication's effects on gut hormone signalling and gastric emptying. Potential contributing factors may include:

• Changes in gastrointestinal motility

• Dietary changes often accompanying weight loss efforts

• Individual digestive system responses to the medication

It is important to note that whilst these gastrointestinal effects are common, they do not indicate that the medication is harmful to the digestive system. Rather, they represent the body's adjustment to altered gut hormone signalling. Most patients find these symptoms diminish significantly after the first few weeks of treatment as tolerance develops, particularly if the dose is increased gradually as recommended in the prescribing information.

Managing Sulphur Burps While Taking Mounjaro

Whilst sulphur burps can be unpleasant and socially embarrassing, several practical strategies can help minimise their occurrence whilst taking Mounjaro. Dietary modification represents the most effective first-line approach to managing this symptom.

Identifying and reducing sulphur-rich foods in your diet can significantly decrease the production of hydrogen sulphide gas. Consider limiting or temporarily avoiding:

• Red meat, particularly beef and lamb

• Eggs and egg-based products

• Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, cabbage)

• Allium vegetables (onions, garlic, leeks)

• Dairy products, especially if lactose intolerant

• Protein supplements, particularly whey-based products

• Certain preservatives (sulphites) found in dried fruits and wine

Eating smaller portions rather than large meals can help reduce the burden on your already-slowed digestive system. This approach minimises the amount of food sitting in the stomach at any one time, thereby reducing gas production. Focus on mindful eating and smaller portions rather than frequent grazing, which may interfere with weight management goals.

Proper eating habits also play a crucial role:

• Eat slowly and chew food thoroughly to aid digestion

• Avoid drinking through straws, which increases air swallowing

• Limit carbonated beverages that introduce additional gas

• Avoid talking whilst eating to reduce air intake

• Remain upright for 30-60 minutes after meals

• Avoid large or high-fat meals that slow digestion further

Over-the-counter remedies may provide symptomatic relief. Antacids containing simeticone can help break up gas bubbles in the digestive tract. Ask your pharmacist for advice on suitable products. Peppermint tea or ginger tea can soothe the digestive system and may reduce belching.

If sulphur burps persist despite these measures, discuss with your GP whether temporarily reducing your Mounjaro dose might be appropriate whilst your body adjusts to the medication.

Treating and Preventing Diarrhoea on Mounjaro

Diarrhoea associated with Mounjaro typically improves within the first few weeks of treatment, but implementing preventive strategies can minimise discomfort during this adjustment period. The approach to managing diarrhoea should balance symptom relief with maintaining adequate nutrition and hydration.

Hydration is paramount when experiencing diarrhoea. Drink enough fluids to keep your urine pale yellow, indicating adequate hydration. Water is ideal, but oral rehydration solutions (available from pharmacies) can help replace lost electrolytes. Avoid excessive caffeine and alcohol, which can worsen dehydration and stimulate bowel movements.

Dietary adjustments can help firm stools and reduce bowel frequency:

• Eat small, light meals that are low in fat and spice

• Include bland foods such as rice, pasta, toast, and bananas

• Increase soluble fibre intake (oats, psyllium husk, cooked carrots) which absorbs water

• Avoid insoluble fibre (raw vegetables, wholegrain cereals) temporarily

• Limit fatty, fried, or spicy foods that can irritate the gut

• Reduce artificial sweeteners (sorbitol, mannitol) which have laxative effects

• Consider a temporary lactose-free diet if dairy worsens symptoms

It's important to continue eating, even if you have diarrhoea, to maintain nutrition.

Probiotic supplementation may help restore gut bacterial balance, though evidence specifically for GLP-1 agonist-related diarrhoea is limited. Discuss with your healthcare provider before starting probiotics, particularly if you have a compromised immune system.

Pharmacological management should be discussed with your healthcare provider. Loperamide (Imodium), available over-the-counter, can be used for short-term symptomatic relief of diarrhoea, usually for up to 48 hours. Seek medical advice if symptoms persist beyond this time. Do not use loperamide if you have blood in your stools, fever, or severe abdominal pain, as these may indicate a more serious condition requiring medical assessment.

Gradual dose escalation of Mounjaro, as recommended in the prescribing information, helps minimise gastrointestinal side effects. If diarrhoea is severe or persistent, your prescriber may recommend remaining at your current dose for an additional week or two before increasing, allowing your digestive system more time to adapt.

Important: If you are also taking insulin or sulfonylurea medications for diabetes, monitor your blood glucose more frequently when experiencing diarrhoea, as reduced food intake could increase your risk of hypoglycaemia. Contact your healthcare provider about possible dose adjustments of these medications.

Maintain a symptom diary noting the frequency and consistency of bowel movements, associated foods, and any other symptoms. This information can be valuable for your healthcare team in determining whether adjustments to your treatment plan are necessary.

When to Seek Medical Advice About Digestive Symptoms

Whilst gastrointestinal side effects are common with Mounjaro and usually resolve with time, certain symptoms warrant prompt medical attention. Understanding when digestive symptoms represent a normal adjustment versus a potentially serious complication is essential for patient safety.

Seek urgent medical attention (contact 999 or attend A&E) if you experience:

• Severe, persistent abdominal pain, particularly if localised to the upper abdomen or radiating to the back, which could indicate pancreatitis—a rare but serious side effect of GLP-1 receptor agonists

• Severe right upper abdominal pain, especially if accompanied by fever or yellowing of the skin/eyes (jaundice), which could indicate gallbladder problems

• Persistent vomiting preventing you from keeping down fluids or medications

• Signs of severe dehydration: extreme thirst, dark urine, dizziness, confusion, or reduced urine output

• Blood in vomit or stools (black, tarry stools or bright red blood)

• Signs of bowel obstruction: severe bloating, inability to pass wind or stools, with vomiting

Contact your GP or NHS 111 within 24 hours if you experience:

• Diarrhoea persisting beyond 7 days despite dietary modifications

• Sulphur burps accompanied by severe nausea or vomiting

• Unintentional weight loss exceeding expected therapeutic effects

• Symptoms significantly impacting your quality of life or ability to work

• New or worsening heartburn or acid reflux

• Difficulty swallowing or sensation of food sticking

People with chronic kidney disease or those taking medications such as diuretics, ACE inhibitors or ARBs should seek advice promptly if experiencing diarrhoea, as dehydration can increase the risk of acute kidney injury.

Routine follow-up should be arranged if:

• Gastrointestinal symptoms are mild but persistent beyond 4 weeks

• You are considering stopping Mounjaro due to side effects (your prescriber may suggest dose adjustment or additional management strategies)

• You have questions about dietary modifications or over-the-counter remedies

According to NICE guidance on diabetes management, regular monitoring and patient education are essential components of treatment with GLP-1 receptor agonists. Your healthcare team should provide clear information about expected side effects and when to seek help. Do not discontinue Mounjaro without consulting your prescriber, as abrupt cessation may affect your glycaemic control or weight management progress.

If gastrointestinal symptoms are intolerable despite optimal management strategies, alternative medications may be available. Your healthcare provider can discuss whether switching to a different GLP-1 receptor agonist, adjusting the dose, or considering alternative therapeutic options might be appropriate for your individual circumstances.

Remember to report any suspected side effects to the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Frequently Asked Questions