Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Starting semaglutide is a big step toward improving your health. But if your stomach hasn’t been cooperating lately, don’t panic. Digestive side effects are common and usually manageable with the right strategies.
Semaglutide, found in brands like Ozempic and Wegovy, mimics a natural hormone called GLP-1 (glucagon-like peptide-1). This hormone helps regulate appetite, blood sugar, and digestion. However, because it slows down how your stomach empties and influences gut hormones, it can lead to some digestive side effects, especially in the first few weeks.
The good news? Most of these side effects tend to improve as your body adjusts, and there are ways to make the process gentler on your stomach.
While everyone’s experience is unique, these are the most frequently reported gut-related effects of semaglutide, backed by clinical studies and real-world reports.
Nausea is the most common complaint by far. In a 2021 study, up to 44% of participants reported nausea during the first month of semaglutide use. It happens as your stomach empties more slowly and your brain’s satiety centres adjust to feeling full faster.
Some people experience vomiting when food lingers too long in the stomach. This is due to delayed gastric emptying, a known pharmacologic effect of GLP-1 receptor agonists.
Loose stools may occur when the gut adjusts to new motility patterns. A review noted diarrhoea in 29.7% of patients starting semaglutide.
Conversely, the slowed intestinal transit can cause constipation. Staying hydrated and gradually increasing fibre helps ease this common side effect.
Bloating occurs as gas builds up in a slower-moving gut. Research suggests that slowed digestion and fermentation of undigested food both play a role.
Stomach cramps are a common yet manageable side effect of semaglutide. They usually occur as your digestive system adjusts to slower movement of food through the gut. As gastric emptying slows down, the intestines may respond with mild spasms: a temporary sign that your GI tract is adapting.
Indigestion, or dyspepsia, can feel like burning, discomfort, or heaviness in your upper abdomen after eating. Since semaglutide delays how quickly food leaves your stomach, it’s no surprise that digestion may feel sluggish in the first few weeks. According to research, these sensations are linked to changes in gut motility and hormone activity.
Acid reflux and heartburn may flare up because of semaglutide’s effect on stomach emptying. When food and stomach acid linger for longer periods, they can more easily rise into the oesophagus. While often mild, this can feel uncomfortable, especially if you eat quickly or lie flat after meals. Reflux tends to improve once the stomach adapts to slower digestion.
Excess gas or flatulence happens as your digestive system adjusts to its new pace. The slowdown allows more fermentation of undigested food in the intestines, producing extra gas. Certain foods like beans, onions, or fizzy drinks can make this worse.
Reduced appetite is actually one of semaglutide’s key benefits. The medication activates GLP-1 receptors in the brain, signalling that you’re full even after smaller meals. Studies confirm that this helps users naturally reduce calorie intake without feeling deprived.
Semaglutide intentionally slows how quickly food leaves the stomach, a process known as delayed gastric emptying. This effect helps with appetite control and blood sugar balance by releasing nutrients more gradually. However, it can also lead to feelings of heaviness or prolonged fullness. This is one of semaglutide’s main physiological mechanisms.
Mild abdominal pain may occur in the early weeks of treatment, especially as your dose increases. The pain might feel like tightness, cramping, or dull pressure, often linked to bloating or constipation. These sensations tend to ease as your body adapts to the medication’s effects on digestion.
Feeling full after just a few bites, known as early satiety, is a hallmark of semaglutide use. Since food stays in your stomach longer, the fullness signal reaches your brain much sooner. This can be helpful for weight management but might make eating a full meal difficult at first.
Heartburn
Heartburn often overlaps with reflux and can create a burning sensation in the chest or throat. Semaglutide can temporarily increase the chance of this happening as your stomach contents linger longer.
A smaller subset of semaglutide users report changes in taste, such as muted flavours or decreased interest in certain foods. Researchers believe this might be linked to shifts in appetite hormones or reduced saliva flow. GLP-1 may interact with taste perception pathways in the brain. While temporary, this can affect your enjoyment of meals.
Dry mouth, or xerostomia, can appear as a secondary effect of nausea or reduced fluid intake. When you eat or drink less, your body produces less saliva, which can cause a dry or sticky feeling in your mouth. It’s important to sip water throughout the day and include hydrating foods like fruit, soup, or yoghurt. Research indicates that GLP-1 agonists may also influence central thirst mechanisms. Staying hydrated can improve not only dry mouth but also constipation and fatigue.
Some people notice more burping while on semaglutide, particularly after meals. A study shows that semaglutide is linked to a significantly high risk of eructation (burping). This is likely connected to semaglutide’s effect on slowing gastric emptying and altering gut motility.
An upset stomach can include mild nausea, queasiness, or general discomfort after eating. It’s one of the body’s natural responses to the slowed digestive process. Research reports that these sensations are most common after dose escalation.
Your bowel habits may shift between diarrhoea and constipation as your gut finds a new balance. This irregularity happens because semaglutide changes how the intestines move and absorb water. A study found that GLP-1 medications can temporarily alter gut motility patterns.
Not everyone experiences digestive symptoms the same way. Here’s why:
Slowed gastric emptying. Semaglutide’s main job is to slow digestion so you feel full longer, but this also means food and gas can linger in your gut.
Changes in gut hormone activity. GLP-1 affects hormones that regulate hunger and digestion, so shifts in these levels can cause temporary discomfort.
Altered appetite signals. Your brain receives new signals about fullness and hunger, which can throw off your usual eating patterns.
Higher starting dose or rapid dose increase. Jumping doses too quickly is a common trigger for intense nausea or vomiting. Gradual titration helps your body adapt.
Sensitivity to fatty or heavy foods. High-fat meals take longer to digest and can worsen symptoms like nausea and bloating.
Dehydration. Semaglutide can reduce thirst, leading to dehydration, which theh worsens constipation, headaches, and dry mouth.
Interaction with other medications. Certain medications (like metformin or antibiotics) can increase gastrointestinal stress when combined with semaglutide.
Individual differences in metabolism. Your body’s ability to process semaglutide, genetics, and gut microbiome all influence how you react.
If your gut is giving you a hard time, these habits can make a big difference.
Start with smaller meals. Eat smaller, more frequent meals instead of three large ones to reduce pressure on your stomach.
Avoid greasy or high-fat foods. These are harder to digest and can trigger nausea or bloating. Opt for lighter, balanced meals instead.
Eat slowly and chew thoroughly. This helps prevent overeating and makes digestion easier for your slowed gut.
Stay hydrated throughout the day. Aim for water or herbal tea rather than soft drinks or coffee, which can irritate your stomach.
Limit alcohol and caffeine. Both can increase acid production and worsen reflux or nausea.
Incorporate more fibre gradually. Fibre helps regulate bowel movements, but introduce it slowly to avoid extra bloating.
Track foods that trigger symptoms. Keep a food diary to identify what worsens or eases your symptoms.
Follow your provider’s dosing schedule carefully. Never rush to a higher dose; it’s better to progress slowly than to deal with severe nausea.
Ask about anti-nausea remedies if needed. If symptoms persist, your doctor might recommend anti-nausea medication or temporary dietary adjustments.
Your digestion might be reacting to more than just the medication. Read this article about whether skipping dinner is good for weight loss to learn how meal timing can affect your gut, appetite, and long-term weight results.
While mild side effects are common, some symptoms need medical attention, including:
Persistent or severe vomiting and diarrhoea
Signs of dehydration (dizziness, dry mouth, little urination)
Severe abdominal pain or suspected pancreatitis
No improvement after several weeks of use
Concerns about possible drug interactions
If you experience sudden, intense abdominal pain or your symptoms worsen despite adjustments, contact your healthcare provider immediately.
Digestive side effects are one of the most talked-about parts of taking semaglutide, but they don’t have to derail your journey. Most symptoms are temporary and can be managed with small lifestyle tweaks, hydration, and patience as your body adjusts.
Understanding how semaglutide affects digestion helps you stay informed, proactive, and confident about your treatment. And if your symptoms become severe or persistent, don’t hesitate to check in with your doctor. They can help you stay on track safely and comfortably.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.