Sulphur burps on Mounjaro and Wegovy are belches with a rotten-egg smell caused by hydrogen sulphide, a gas produced when bacteria in the gut break down sulphur-containing food. These medicines slow how quickly the stomach empties, so food stays in the digestive tract for longer and more gas can form. Burping (eructation) is listed as a common side effect in the UK product information, and it usually settles as your body adjusts. Eating smaller, slower meals, spacing out trigger foods, avoiding fizzy drinks and not lying down after eating often help. See a clinician if burps persist for weeks or come with pain, vomiting, black stools or weight loss that you did not expect.
Sulphur burps, sometimes called egg burps, are belches that smell of rotten eggs. The smell comes from hydrogen sulphide, a gas that is produced when bacteria in the gut break down sulphur-containing compounds in food, particularly proteins and some vegetables. Small amounts of hydrogen sulphide are made in everyone’s gut all the time. You notice them when more gas is produced than usual, or when it is brought back up as a belch rather than passing downwards as wind.
They are not dangerous in themselves. They are, however, a signal that something about digestion has changed, and it is worth understanding why, particularly if they are persistent or come with other symptoms.
Why GLP-1 medicines can cause themMounjaro (tirzepatide) and Wegovy (semaglutide) copy gut hormones that slow gastric emptying, meaning the stomach releases its contents into the intestine more slowly. This is part of why you feel full sooner and for longer. It also means food stays in the stomach and upper gut for longer than usual, which gives bacteria more time and more material to work on.
- Slower stomach emptying means more time for food to ferment and release gas.
- Eating less overall, but still eating protein-rich or sulphur-rich foods, can concentrate the effect.
- Reflux and a slower gut can bring gas and stomach contents back up as belching.
- The effect is often strongest when you start treatment and after each dose increase, then eases as your body adjusts.
The UK product information for Mounjaro lists eructation (belching), flatulence, abdominal distension and gastro-oesophageal reflux disease among the common side effects. For Wegovy, belching, wind and reflux are also listed, and the product information notes that these gastrointestinal effects are seen mainly during the dose-escalation period. In other words, they are an expected effect of how the medicines work, not a sign of an allergy or a faulty pen.
Common triggersFood and drink do not cause the problem on their own, but certain ones make sulphur gas more likely, especially when digestion is slow. Keeping a short food diary for a week or two can show which ones matter for you.
| Trigger | Why it can contribute | What to try |
|---|---|---|
| Eggs | Rich in sulphur-containing protein | Smaller portions; try other protein, such as fish or tofu, at the same time of day |
| Red meat and processed meat | Protein and preservatives that bacteria ferment | Smaller portions, slower eating |
| Whey protein shakes | Concentrated protein, often with sweeteners | Try a smaller scoop, a different brand or food-first protein |
| Cruciferous vegetables (broccoli, cabbage, cauliflower, Brussels sprouts) | Contain sulphur compounds | Cook well, smaller portions, space them out |
| Garlic and onions | Contain sulphur compounds and fermentable carbohydrates | Smaller amounts, or use infused oil instead |
| Fizzy drinks and beer | Add gas to the stomach | Still or flat drinks, sipped slowly |
| Red wine and dried fruit | Often contain sulphites | Limit and see if symptoms ease |
| Sugar alcohols (sorbitol, xylitol) in sugar-free products | Poorly absorbed and fermented in the gut | Check labels on sweets, gum and protein bars |
| Large or fatty meals | Slow emptying further | Smaller, lower-fat meals |
DO NOT CUT OUT PROTEIN
Protein is important for protecting muscle during weight loss, so do not stop eating it because of burps. Instead, adjust the type, portion size and timing, and consider spreading protein across the day. Our protein guide explains targets and options.
Change how you eat
- Eat smaller meals and stop when you feel comfortably full, which can arrive sooner than before.
- Eat slowly and chew thoroughly, which reduces swallowed air and helps digestion.
- Avoid talking and eating at the same time, and avoid drinking through straws, which also increase swallowed air.
- Leave 2 to 3 hours between your last meal and lying down, and avoid late-night eating.
- Walk gently for 10 to 15 minutes after meals, which can help move food through the gut.
Adjust triggers rather than removing food groups
- Keep a food and symptom diary for one to two weeks, noting what you ate before a bout of burps.
- Pause one suspected trigger at a time rather than cutting many foods at once.
- Reintroduce foods in smaller portions once you feel better. Many people can eat their trigger foods in moderation.
- Spread vegetables and high-protein foods across meals rather than eating them together in large amounts.
Drinks
- Sip fluids steadily through the day rather than drinking large amounts with meals.
- Choose still water or herbal teas over fizzy drinks.
- Limit alcohol, which can aggravate reflux and slow digestion.
Reflux and wind
If burps come with heartburn or a sour taste, simple measures such as smaller meals, avoiding late eating and raising the head of the bed may help. Your pharmacist can advise on over-the-counter products for wind or indigestion that suit your other medicines and health conditions. Our guide to diarrhoea, bloating and reflux covers these in more detail. Do not take antacids or other remedies regularly for weeks without checking, because persistent symptoms deserve a proper look.
What to avoid- Skipping meals to avoid symptoms. Eating too little can worsen tiredness, dizziness and nutrient gaps.
- Taking large doses of supplements or home remedies without advice.
- Cutting dose or skipping injections without speaking to your prescriber. If symptoms are troublesome, your prescriber may suggest staying longer on a dose before increasing.
- Assuming it is harmless if it persists, gets worse or arrives with other symptoms.
There is no fixed timeline. Many people find that belching and sulphur burps are worst in the first weeks and after a dose increase, then ease over days to weeks as the body adjusts and as food and eating habits settle. If they are still frequent after about a month on a stable dose, or they are getting worse, it is worth raising with your pharmacist or prescriber.
| Pattern | What it may suggest | What to do |
|---|---|---|
| Starts after a dose increase, eases within a few weeks | Expected gut adjustment | Smaller meals, trigger diary, patience |
| Linked to certain foods | Food trigger | Reduce portions, adjust timing |
| With heartburn or sour taste | Reflux | Late eating changes; ask your pharmacist about options |
| Persists beyond a month on a stable dose | Needs review | Speak to your prescriber or GP |
| With severe pain, repeated vomiting or black stools | Possible serious problem | Seek urgent medical help |
Not every case of sulphur burps is caused by a GLP-1 medicine. Other conditions can cause similar symptoms, which is why persistent or worsening burps deserve a check.
- Helicobacter pylori infection of the stomach, which can cause indigestion, belching and sometimes nausea.
- Gastro-oesophageal reflux disease and gastritis.
- Intolerance to certain foods, such as lactose or fructose.
- Gut infections, such as giardia, which is classically linked to foul-smelling burps and diarrhoea, especially after travel.
- Irritable bowel syndrome and small intestinal bacterial overgrowth.
- Gallbladder problems, which can cause upper abdominal discomfort and bloating, and which are more common with rapid weight loss.
SPEAK TO A CLINICIAN
Seek advice if sulphur burps last more than a few weeks, or come with persistent vomiting, severe or worsening upper abdominal pain that may spread to the back, yellowing of the skin or eyes, black or bloody stools, difficulty swallowing, or weight loss that is faster than expected. Severe abdominal pain with repeated vomiting needs urgent help, because pancreatitis and gallbladder problems are rare but serious side effects.
| Symptom | Why it matters | Action |
|---|---|---|
| Severe upper abdominal pain, spreading to the back | Possible pancreatitis | Seek urgent help |
| Repeated vomiting or inability to keep fluids down | Risk of dehydration | Contact your prescriber urgently |
| Black, tarry or bloody stools | Possible bleeding | Seek urgent medical help |
| Yellow skin or eyes, dark urine | Possible liver or gallbladder problem | Seek urgent medical help |
| Difficulty or pain swallowing | Needs assessment | See your GP promptly |
| Persistent burps beyond a month | Needs review | Speak to your prescriber or GP |
- Could my dose or titration speed be contributing?
- Which over-the-counter products are suitable alongside my medicines?
- Should I be tested for Helicobacter pylori or other causes?
- Is my protein intake and the type of protein suitable?
- How long should I wait before I worry?
The bottom line
Sulphur burps on Mounjaro and Wegovy are an unpleasant but usually harmless digestive side effect, caused by slowed stomach emptying and bacteria producing hydrogen sulphide. They tend to be worst when starting and after dose increases, and they often settle with smaller, slower meals, a food diary to spot triggers, fewer fizzy drinks and a short walk after eating. Keep eating protein, adjust rather than eliminate foods, and speak to a clinician if burps persist beyond a few weeks or arrive with pain, vomiting, black stools or unexpected weight loss.
Struggling with digestive side effects?
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Start Your Free Online Consultation Use code SWITCH10 if you're switching from another provider Happy Pharmacy is a GPhC-registered pharmacy (No. 9013192). Superintendent Pharmacist: Palvinder Deol. Rated 4.8★ Excellent on TrustpilotMedical disclaimer. This guide is for general information and is not a substitute for personal medical advice. Weight-loss medicines are prescription-only and are not suitable for everyone. Always follow the patient information leaflet and the advice of your prescriber or pharmacist.
- Mounjaro (tirzepatide) KwikPen: UK Summary of Product Characteristics, sections 4.4 and 4.8. electronic Medicines Compendium (emc).
- Wegovy (semaglutide) solution for injection in pre-filled pen: UK Summary of Product Characteristics, sections 4.4 and 4.8. emc.
- NHS. Indigestion: symptoms, causes and treatments.
- NHS. Heartburn and acid reflux.
- NICE Clinical Knowledge Summaries. Dyspepsia: proven and Helicobacter pylori infection.
- Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society. 2025.