Why do I get sulphur burps on Mounjaro or Wegovy?

Burping is a listed side effect of both. The patient leaflets put it among the common side effects, affecting up to 1 in 10 people. Nobody has studied why the burps can smell of rotten eggs on these medicines. What is known is that the smell comes from sulphur gases, mainly hydrogen sulphide, which gut bacteria make when they break down food, especially protein, and that these medicines slow digestion.

How long do sulphur burps last on Mounjaro or Wegovy?

There is no published figure for burping specifically. In the trials, stomach side effects such as nausea, vomiting and diarrhoea were most common while the dose was being increased and became less common over time. If you keep getting indigestion, the NHS advises seeing a GP.

What should I eat if I get sulphur burps on a GLP-1?

The NHS advice for indigestion and wind is to eat smaller meals more often, eat slowly, avoid rich, spicy or fatty food, not eat in the 3 to 4 hours before bed, and cut down on fizzy drinks, alcohol, tea and coffee. Foods that commonly cause wind include cabbage, broccoli, cauliflower, Brussels sprouts, onions, beans, lentils, dried fruit and the sweetener sorbitol. Keep eating protein, but spread it across the day rather than in one large meal.

Why can't I eat salad any more on a GLP-1?

No study has looked at salad on GLP-1 medicines, so nobody can say for sure. These medicines slow digestion, and a large bowl of raw vegetables is a lot of bulk to process. Some people find smaller portions, or cooked vegetables, sit better. Treat it as an experiment: try a smaller salad, or the same vegetables cooked, and see what happens.

When are burps and gas on a GLP-1 a reason to see a doctor?

See a GP if you keep getting indigestion, are in severe pain, keep being sick, have difficulty swallowing, or have blood in your vomit or poo. Call NHS 111 if bloating comes with vomiting, diarrhoea or a stomach ache, and call 999 for a sudden, severe stomach ache or vomit that looks like coffee grounds. Severe pain in your stomach or back that does not go away can be a sign of an inflamed pancreas.

Sulphur Burps on Mounjaro or Wegovy: What Helps

The 30-second summary

Burping, wind and bloating are listed side effects. The patient leaflets for Mounjaro and Wegovy put them among the common ones, affecting up to 1 in 10 people.

The eggy smell comes from sulphur gases, mainly hydrogen sulphide, made by gut bacteria as they break down food. Nobody has yet studied why these medicines bring it on.

Smaller meals, less fat, fewer fizzy drinks and nothing late at night is the NHS advice for indigestion and wind. See a doctor if it keeps happening or comes with severe pain or vomiting.

How common it is

Burping is not an internet myth. It is written into the prescribing information.

Wegovy. The patient leaflet lists upset stomach or indigestion, burping, gas and bloating among the common side effects, which it defines as affecting up to 1 in 10 people. In the US prescribing information, 7% of adults on the Wegovy injection in the weight-loss trials reported burping, against under 1% on placebo, and 6% reported wind, against 4%.
Mounjaro. The prescribing information lists indigestion, bloating, burping, wind and reflux as common side effects. In one large trial of tirzepatide in people with type 2 diabetes, 5.4% reported burping and 4.8% wind.

The label does not say how long burping lasts. For the side effects the trials measured in detail, such as nausea, vomiting and diarrhoea, the pattern was the same for both medicines: most common while the dose was being increased, and less common over time. (See nausea on a GLP-1.)

Why the burps can smell of eggs

The rotten-egg smell is the smell of sulphur gases.

A 1998 study in Gut measured the gases in intestinal wind and found that the main sulphur gas was hydrogen sulphide, and that the bad smell rose with how much hydrogen sulphide there was. Those gases are made by bacteria in the gut. A controlled feeding study in 2000 found that the more meat people ate, the more sulphide their gut bacteria produced, with protein as the raw material.

Why GLP-1 medicines bring this on has not been studied. What we do know is that they slow digestion: the NHS says both semaglutide and tirzepatide slow digestion, and delayed stomach emptying is listed in both labels. Food that stays in the gut longer gives bacteria longer to work on it, which is a plausible explanation. Plausible is all it is for now, so treat any confident claim about the cause with care.

What helps

The NHS pages on indigestion, wind and bloating give practical advice that fits well here.

Do:

Eat smaller meals, more often.
Eat and drink slowly, with your mouth closed, so you swallow less air.
Keep moving. Regular exercise helps digestion.
Try peppermint tea.
Raise your head and shoulders in bed if acid comes up at night.

Don't:

Eat in the 3 to 4 hours before bed.
Have rich, spicy or fatty food.
Drink lots of fizzy drinks, beer or alcohol, or too much tea, coffee or cola.
Chew gum, which makes you swallow air.
Take ibuprofen or aspirin unless they have been prescribed, as they can make indigestion worse.

A 2025 joint advisory on nutrition for GLP-1 treatment, from four US nutrition and obesity medicine societies, adds that avoiding large or high-fat meals can help with diarrhoea, which some people get alongside sulphur burps.

What to eat, and what to go easy on

Foods the NHS lists as ones that make you fart: cabbage, broccoli, cauliflower, Brussels sprouts, onions, pulses such as beans and lentils, dried fruit such as raisins or apricots, the sweetener sorbitol, and fizzy drinks and beer.

Sorbitol is easy to miss, so check ingredients lists for it.

Protein is not the enemy. You still need it, and plenty of it, to protect muscle while you lose weight. (See protein on a GLP-1.) But if one large, meat-heavy meal is followed by a bad evening, try the same amount of protein spread across the day, in smaller portions, and see whether it helps. The feeding study above suggests meat is a major source of the raw material for sulphide, though it measured the colon, not the stomach, so this is an experiment rather than a rule.

Fibre still matters, because constipation is one of the most common side effects of all. Have it with plenty of fluid. For constipation, the NHS suggests foods high in soluble fibre, such as oats or linseed. (See fibre on a GLP-1 and constipation on a GLP-1.)

"I can't eat salad any more"

This comes up again and again: a salad that was fine before the medicine now brings on wind, burps and discomfort.

No study has tested salad on GLP-1 medicines, so there is no evidence-based answer. Two things are true, though. These medicines slow digestion, and a large bowl of raw vegetables is a lot of bulk. Several of the vegetables most often found in salads and slaws, such as cabbage, onions and broccoli, are on the NHS list of foods that cause wind.

So experiment rather than give vegetables up. Try a smaller portion, leave out the onion or cabbage, or eat the same vegetables cooked, and notice what makes a difference for you. If it is only certain vegetables, you have learned something useful. If it is everything, and it is not easing, mention it to your prescriber.

What a pharmacist can suggest

Before you buy anything, it is worth a conversation with a pharmacist, and telling them you take a GLP-1 medicine. According to the NHS, they may suggest:

For indigestion: antacids, alginates or proton pump inhibitors.
For wind and bloating: simeticone.

If you find you need these most days, tell your prescriber. Persistent symptoms can be a reason to hold a dose increase for longer. (See pausing a dose increase.)

When it is not just wind

Most burping and wind is unpleasant rather than dangerous. The NHS gives clear lines for when it is more than that.

See a GP if you:

keep getting indigestion, or are in severe pain
keep being sick
have difficulty swallowing
have blood in your vomit or poo
have bloating that keeps coming back or will not go away

Ask for an urgent GP appointment or call NHS 111 if you have bloating with:

vomiting, diarrhoea or constipation
a stomach ache
a high temperature, or you feel hot, cold or shivery
you cannot pee, poo or fart

Call 999 or go to A&E if you have a swollen stomach with a sudden, severe stomach ache, or your vomit contains blood or looks like ground coffee.

Also know the GLP-1 specific warning signs. The NHS lists severe pain in your stomach or back that does not go away as a sign of an inflamed pancreas, and severe tummy pain from gallstones among the rare but serious side effects of tirzepatide. If you keep being sick and cannot keep fluids down, call NHS 111. Outside the UK, call your local emergency number.

What to do with this

Smaller, more frequent meals only work if each one still carries enough protein. The calculator works out your protein floor and how much you are likely to manage at your dose, so you can split the day into portions your stomach will put up with.

Get your numbers

Sources

Wegovy FlexTouch: Package leaflet, information for the patient. electronic medicines compendium. emc
US Food and Drug Administration. WEGOVY (semaglutide) injection and tablets: Prescribing Information, 2026. FDA label
Mounjaro KwikPen solution for injection in pre-filled pen: Summary of Product Characteristics. electronic medicines compendium. emc
Suarez FL, et al. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour. Gut 1998. PubMed
Magee EA, et al. Contribution of dietary protein to sulfide production in the large intestine: an in vitro and a controlled feeding study in humans. Am J Clin Nutr 2000. PubMed
NHS. Indigestion. nhs.uk
NHS. Farting (flatulence). nhs.uk
NHS. Bloating. nhs.uk
NHS. Semaglutide. nhs.uk
NHS. Tirzepatide. nhs.uk
Mozaffarian D, et al. 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. Obesity Pillars 2025. PubMed
Wharton S, et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss. Diabetes Obes Metab 2022. PubMed

Medical disclaimer: Articles in the foodose research library are educational, not medical advice. Talk to your prescriber or pharmacist about side effects that bother you. See our full medical disclaimer.

Sulphur burps and gas on Mounjaro or Wegovy: why they happen, and what helps