This guide explains what sulphur burps are, why they can happen on Mounjaro, how to manage them, and when to speak to your healthcare provider.

What are sulphur burps?

Sulphur burps occur when gas containing hydrogen sulphide (H₂S) escapes during a burp. This gas forms naturally in the digestive tract when certain sulphur-containing compounds, most commonly from food, are broken down by gut bacteria.

While small amounts of H₂S are harmless, its strong odour can be socially awkward and unpleasant. Sulphur burps are a normal digestive occurrence for many people from time to time, but in some situations (including with Mounjaro use) they can become more frequent.

Why Mounjaro can cause sulphur burps

Sulphur burps are not listed specifically in the Mounjaro Summary of Product Characteristics (Eli Lilly, 2024) or the FDA Prescribing Information (FDA, 2022). However, Mounjaro is associated with a range of GI side effects, including nausea, belching, bloating, and constipation, that can contribute to or trigger sulphur burps.

The most likely mechanisms include:

a) Slower gastric emptying

Tirzepatide slows the rate at which food leaves the stomach (Frias et al., 2021). This is part of its appetite-suppressing effect, but it also means food remains in the stomach longer, giving bacteria more time to break down sulphur-rich foods and produce H₂S gas.

b) Dietary changes

People on Mounjaro often make significant shifts in eating patterns; smaller portions, higher protein intake, or increased vegetable consumption. Some of these foods (eggs, garlic, onions, broccoli, cauliflower, Brussels sprouts) naturally contain more sulphur compounds, which can fuel H₂S production.

c) Altered gut microbiota

Emerging research suggests GLP-1 receptor agonists may influence the gut microbiome (Smits et al., 2022). Even small shifts in bacterial populations can change gas composition and odour.

d) Slowed bowel transit and constipation

Constipation is reported in 6–7% of Mounjaro users in clinical trials (FDA, 2022). When food residues move more slowly through the colon, bacterial fermentation has more time to produce gas, including sulphur gas.

How common is it?

While sulphur burps aren’t recorded as a standalone side effect in Mounjaro trials, related symptoms give us clues:

• Nausea: 12–18% of patients (SURPASS-2; Frias et al., 2021)
  
  
• Belching/eructation: reported but not quantified separately in trial publications
  
  
• Constipation: 6–7% (SURMOUNT-1; Jastreboff et al., 2022)
  
  

Given these figures, sulphur burps likely represent a subset of GI complaints, particularly in the early treatment phase or after dose increases.

When sulphur burps tend to appear

Based on trial observations of GI events and patient-reported experiences, sulphur burps are most likely to occur:

• In the first 2–4 weeks after starting Mounjaro
  
  
• Within days of a dose escalation
  
  
• After meals high in protein or sulphur-containing vegetables
  
  
• During episodes of constipation or reduced fluid intake
  
  

When are sulphur burps a concern?

For most Mounjaro users, sulphur burps are harmless and temporary. They often fade within a few weeks as the body adjusts.

However, you should seek medical advice if burps are accompanied by:

• Persistent vomiting or diarrhoea
  
  
• Severe or worsening abdominal pain
  
  
• Fever or other signs of infection
  
  
• Difficulty swallowing or unexplained weight loss
  
  
• Signs of dehydration (dizziness, dark urine, dry mouth)
  
  

Persistent sulphur burps can sometimes be linked to infections such as Giardia lamblia, peptic ulcer disease, or other GI conditions (Levitt et al., 2012).

How to reduce or prevent sulphur burps on Mounjaro

Clinical guidance for GLP-1-related GI side effects can be adapted to manage sulphur burps.

Adjust your diet

• Limit high-sulphur foods (at least temporarily): eggs, garlic, onions, broccoli, cauliflower, cabbage, sprouts.
  
  
• Reduce high-fat meals, which slow digestion further (FDA, 2022).
  
  
• Avoid very large meals, smaller portions are easier to digest.
  
  

Eat smaller, more frequent meals

Instead of three large meals, aim for 4–5 smaller meals spaced throughout the day. This keeps gastric contents lower in volume and may reduce fermentation.

Stay well hydrated

Aim for 1.5–2 litres of fluids daily, unless otherwise advised. Hydration supports gut motility and can reduce constipation-related gas build-up.

Support digestion through movement

• Light walking after meals can stimulate gastric emptying and intestinal movement (Camilleri et al., 2017).
  
  
• Avoid lying down immediately after eating to reduce reflux and burping.
  

Adjust your injection timing

Some people find that taking Mounjaro in the morning rather than at night reduces digestive side effects, although no formal trial has tested this specifically for sulphur burps.

Manage constipation proactively

• Increase fibre gradually (oats, psyllium, inulin) to avoid worsening bloating.
  
  
• Consider an osmotic laxative if advised by your healthcare provider.
  

Natural and over-the-counter options

While no studies have examined treatments for Mounjaro-specific sulphur burps, some interventions have evidence for improving GI comfort more generally:

• Peppermint oil — proven to help bloating and functional GI discomfort (Cash et al., 2016).
• Ginger — may enhance gastric emptying and reduce nausea (Hu et al., 2011).
• Simethicone — reduces surface tension in gas bubbles, making them easier to pass.
  
  

Always check with a pharmacist or GP before starting any supplement or medication alongside Mounjaro.

How long do sulphur burps last?

For most users, sulphur burps improve significantly within 6–8 weeks as the digestive system adapts to slower gastric emptying. If they persist beyond this, it’s worth reviewing your dose, diet, and possible underlying causes with your prescriber.

Final thoughts

Sulphur burps can be an unpleasant surprise for some people starting Mounjaro, but they are usually temporary and manageable.

By adjusting diet, improving hydration, supporting gut motility, and managing constipation, most people can reduce or eliminate sulphur burps without interrupting treatment.

If symptoms persist or worsen, don’t stop Mounjaro without guidance. Your healthcare provider can work with you to find a comfortable, sustainable balance.