The most common side effects of Ozempic are gastrointestinal: nausea, vomiting, diarrhea, constipation, and stomach pain. These affect a significant portion of users, especially during the first weeks of treatment, and they stem directly from how the drug works in your body. Most are manageable and fade over time, but some rarer effects deserve attention.
Why Ozempic Causes Stomach Problems
Ozempic (semaglutide) works by mimicking a hormone your gut naturally releases after eating. This hormone activates receptors in three key places: the pancreas, where it triggers insulin release; the brain’s hunger centers, where it creates a feeling of fullness; and the stomach’s nerve cells, where it slows digestion. That slowdown is central to the drug’s weight loss effect, keeping food in your stomach longer so you feel satisfied with less. But it’s also the direct cause of the nausea and vomiting that top the side effect list.
Think of it this way: your stomach is holding onto food longer than your body expects. That prolonged fullness can register as nausea, especially after larger meals. For some people it’s mild queasiness that passes in a few weeks. For others it’s persistent enough to interfere with daily life.
Common Side Effects in the First Few Months
The gastrointestinal effects are by far the most frequently reported. They include:
- Nausea: the single most common complaint, often worst in the first four to eight weeks
- Vomiting and diarrhea: less frequent than nausea but still common
- Constipation: slowed digestion can swing both ways
- Abdominal pain and bloating: from food sitting in the stomach longer than usual
Ozempic’s dosing schedule is specifically designed to reduce these effects. You start at the lowest dose for four weeks before stepping up, giving your body time to adjust. Eating smaller meals, avoiding high-fat foods, and stopping eating when you first feel full can also help. Most people find their stomach symptoms improve noticeably after the first couple of months, though some experience flare-ups each time the dose increases.
Gallbladder Problems
Rapid weight loss from any cause increases the risk of gallstones, and Ozempic is no exception. A meta-analysis pooling data from eight randomized trials found that about 3% of people taking semaglutide experienced gallbladder problems, compared to 2.2% on placebo. The risk of gallstones specifically was even more pronounced: 2.3% of semaglutide users developed them versus 0.9% in the control group, a roughly 2.5-fold increase.
Gallstones don’t always cause symptoms. When they do, you’ll typically feel sudden, intense pain in the upper right side of your abdomen, sometimes radiating to your back or right shoulder. This pain often strikes after eating and can last from minutes to hours. If gallstones block a duct and cause inflammation of the gallbladder itself, the pain becomes more severe and persistent, sometimes accompanied by fever.
Facial Changes and Muscle Loss
The term “Ozempic face” has become widely recognized, but it’s not a direct side effect of the medication. It’s a consequence of rapid weight loss. Your face gets its youthful, filled-in appearance partly from a layer of fat just beneath the skin. Losing weight quickly depletes that fat, while also lowering levels of the proteins that keep skin stretchy and structurally supported: elastin and collagen. The result is facial hollowing and sagging that can make you look older than you did before treatment, even if your overall health has improved.
This mimics the natural aging process but at an accelerated pace. Everyone loses facial fat as they get older, but dropping a large amount of weight in a short period compresses years of that change into months.
There’s also been concern about losing muscle along with fat. Research from the University of Utah found that semaglutide-induced weight loss decreased lean mass by about 10%, but most of that came from organs like the liver (which shrank by nearly half) rather than skeletal muscle. Actual skeletal muscles shrank by about 6% on average. Still, preserving muscle during weight loss matters for long-term metabolic health, and resistance training while on the medication is widely recommended.
Pancreas and Thyroid Risks
Pancreatitis, or inflammation of the pancreas, is listed as a warning on Ozempic’s label. It’s rare, but it’s serious. Symptoms include severe abdominal pain that radiates to the back, often with nausea and vomiting that doesn’t improve. Post-marketing reports have documented cases of both acute and necrotizing pancreatitis in people taking semaglutide, with some cases resulting in death. If you develop sudden, severe stomach pain that feels different from the usual gastrointestinal discomfort, that warrants immediate medical attention.
The thyroid concern is more nuanced. In animal studies, semaglutide caused thyroid tumors in rodents, which is why the drug carries a boxed warning about medullary thyroid carcinoma. In humans, the picture is less alarming. A large Scandinavian cohort study found no statistically significant increase in medullary thyroid cancer risk among people using GLP-1 drugs like Ozempic. The drug remains contraindicated for anyone with a personal or family history of medullary thyroid carcinoma or a rare condition called Multiple Endocrine Neoplasia syndrome type 2.
Eye Health for People With Diabetes
If you’re taking Ozempic for type 2 diabetes and already have some degree of diabetic retinopathy, this one matters. In a two-year trial of patients with diabetes and high cardiovascular risk, 3% of those on Ozempic experienced diabetic retinopathy complications compared to 1.8% on placebo. The gap was wider among people who already had retinopathy at the start of the study: 8.2% versus 5.2%.
The likely explanation is that rapid improvements in blood sugar control can temporarily worsen existing retinopathy, a phenomenon that’s been documented with insulin therapy as well. It doesn’t mean Ozempic damages your eyes directly, but it does mean more frequent eye exams are important if you have a history of diabetic eye disease.
Mental Health Effects
Early reports raised concerns that Ozempic and similar drugs might increase the risk of suicidal thoughts or depression. The FDA investigated this thoroughly and concluded there is no increased risk. After controlling for pre-existing conditions, the agency found no elevated risk of suicidal ideation, intentional self-harm, anxiety, depression, irritability, or psychosis in people using GLP-1 medications compared to other diabetes drugs. Based on these findings, the FDA in 2025 requested that manufacturers remove suicidal behavior warnings from GLP-1 drug labels.
Effects on Other Medications
Because Ozempic slows how quickly your stomach empties, it can change how your body absorbs other medications you take by mouth. Pills that depend on being absorbed at a predictable rate, including some birth control pills, blood pressure medications, and antibiotics, may not work the same way. This doesn’t mean they stop working entirely, but the timing and intensity of their effects can shift. If you take medications where precise absorption matters, that’s worth discussing when starting Ozempic.
Ileus: A Rare but Serious Complication
Post-marketing reports have also identified ileus, a condition where the normal muscular contractions of the intestine temporarily stop, causing a bowel obstruction. This is rare but can be dangerous. Symptoms include severe bloating, cramping, inability to pass gas or have a bowel movement, and vomiting. The slowed gastric emptying that Ozempic causes may also pose risks during surgery or procedures requiring sedation, because food retained in the stomach can be aspirated into the lungs.