Wegovy, Sulphur Burps and Diarrhoea: What's Happening and When It Usually Settles

Step 1: Understand why semaglutide causes these symptoms in the first place

Semaglutide activates GLP-1 receptors in the gut and the brain, which slows gastric emptying — the rate at which food leaves your stomach and enters the small intestine. That mechanism is central to how the medicine reduces appetite. The side effect, though, is that food sitting longer in your digestive tract gives bacteria more time to ferment it, and that fermentation produces hydrogen sulphide gas. If you want to understand more about how sulphur burps develop for people taking Wegovy, the result is those distinctively unpleasant egg-smelling burps that many people on Wegovy describe.

Diarrhoea follows a related but slightly different path. Altered gut motility affects fluid absorption in the intestine; some people's systems respond by moving things through faster rather than slower, which is why Wegovy can cause both constipation and diarrhoea, sometimes alternating. The NHS medicines page for semaglutide lists diarrhoea and burping among the common side effects, meaning they affect between one in ten and one in hundred users, some estimates from clinical trial data put the rate considerably higher during the first weeks of use.

Understanding the mechanism matters because it changes how you respond. These aren't random reactions; they're predictable consequences of how the medicine works, which means they're often manageable with adjustments to what and how you eat. More on why semaglutide specifically triggers sulphur-smelling belching is covered in a dedicated explainer if you want the fuller picture.

Step 2: Identify the foods and habits most likely to be making it worse

Not all meals create equal amounts of sulphur gas. Foods that are high in sulphur compounds (eggs, red meat, dairy, cruciferous vegetables like broccoli, cauliflower and cabbage) give gut bacteria more raw material to work with. On a normal digestive schedule that's usually fine. When gastric emptying is slowed by semaglutide, those same foods spend longer fermenting, and the gas production scales up accordingly.

Fatty meals are a double problem: fat is the macronutrient that most potently triggers further GLP-1-mediated slowing, so a high-fat meal on Wegovy can compound the delayed emptying that's already happening. Eating too quickly, or in larger portions than your now-reduced appetite actually wants, adds extra pressure on a system that's already working more slowly than usual.

Practical adjustments that many people on semaglutide find helpful include: smaller, more frequent meals rather than two or three large ones; reducing the sulphur-rich foods listed above temporarily around dose-change weeks; eating slowly and stopping well before any feeling of fullness; and staying well hydrated, which helps move things through when diarrhoea is the main complaint. Specific strategies for reducing sulphur burps on Wegovy go into more detail on each of these, including timing meals around injection days.

One thing worth knowing: symptoms often cluster around particular life moments, a long weekend of richer food, or the adjustment period that follows a dose step-up. A number of people who restart treatment after a break (holidays being the obvious one) notice a return of early symptoms, because the gut goes through a fresh adjustment. That's normal, and it usually passes faster the second time.

Step 3: Track how long the symptoms last and when to speak to someone

For most people starting Wegovy, the worst of the GI symptoms land in the first one to four weeks of a new dose. After that, the majority see a noticeable improvement as the gut adapts. How long sulphur burps typically last on Wegovy is covered in detail elsewhere; the short answer is that persistent symptoms beyond four to six weeks at a stable dose are worth raising with your prescriber, because titration timing or dietary adjustments may help.

Diarrhoea that is severe enough to cause dehydration (think significant thirst, dizziness, or very dark urine) needs medical attention sooner. The same applies to diarrhoea that is accompanied by signs of an allergic reaction, or that begins suddenly and severely after weeks of no problems. A closer look at the diarrhoea and sulphur burps combination on semaglutide covers the overlap between these two symptoms and what tends to drive each one.

For the broader picture of GI and other reactions, the full Wegovy side effects page covers each one with the same level of detail.

When to get medical help, and what the MHRA flags as urgent

Most sulphur burps and loose stools on Wegovy are uncomfortable rather than dangerous. There are, however, symptoms that need prompt attention and should not be waited out.

Seek urgent medical help if you experience severe stomach pain, particularly pain that is persistent and radiates to your back, with or without vomiting. This is a recognised warning sign of acute pancreatitis, which the MHRA highlighted as an infrequent but serious risk associated with GLP-1 medicines in a Drug Safety Update published in January 2026. Pancreatitis is rare, but it is serious enough that it cannot be managed at home.

Also seek help for: signs of a severe allergic reaction (swelling of the face or throat, difficulty breathing); symptoms of significant dehydration from persistent diarrhoea or vomiting; and any sudden or worsening symptoms that feel clearly out of proportion to the usual adjustment pattern.

If you suspect a side effect that isn't listed in your Patient Information Leaflet, or one that seems more severe than expected, you can report it directly through the MHRA's Yellow Card scheme. That reporting helps regulators monitor the real-world safety profile of medicines like Wegovy across the population, it's a genuinely useful thing to do, not just a formality.

Our prescribers discuss side effect management, suitability, and what to watch for as a normal part of every consultation. If you're weighing up whether Wegovy is right for you, speaking to our prescribers is the place to start.