Semaglutide side effects, and how to manage them

Common semaglutide side effects

Semaglutide is the active ingredient in Wegovy and Ozempic. Most semaglutide side effects come from the way it slows stomach emptying and acts on appetite centers in the brain. They tend to appear in the first weeks and after each dose increase, then ease for many people as the body adapts.

In clinical trials, digestive symptoms were the most frequently reported effects. Most were mild to moderate, though a small proportion of people stopped treatment because of them.

• Nausea, especially after large or fatty meals
• Constipation, sometimes alternating with diarrhea
• Vomiting, bloating, burping or indigestion
• Fatigue, headache or dizziness, often linked to eating and drinking less
• Early fullness and reduced appetite, which is part of how the medicine works

Less common but important risks

Gallbladder problems. Rapid weight loss and semaglutide itself are linked to a higher risk of gallstones and gallbladder inflammation. Pain in the upper right abdomen, especially after meals, fever or yellowing of the skin or eyes should be checked.

Pancreatitis. Acute pancreatitis has been reported with GLP-1 medicines. It is uncommon, but it is serious. The classic sign is severe, persistent upper abdominal pain that may spread to the back, with or without vomiting. Semaglutide should be stopped and not restarted if pancreatitis is confirmed.

Thyroid C-cell tumor warning. Semaglutide carries a boxed warning because it caused thyroid C-cell tumors in rodents. It is not known whether this happens in humans. It must not be used by anyone with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN2). Report a lump in the neck, hoarseness, trouble swallowing or shortness of breath.

Low blood sugar. Semaglutide alone rarely causes hypoglycemia, but the risk rises when it is combined with insulin or sulfonylureas. These medicines often need a lower dose. Other reported risks include kidney strain from dehydration, worsening diabetic eye disease in people with diabetes, and increased heart rate.

How we reduce side effects at VEI Clinic

Dr. HyunSung Park, an internal medicine and gastroenterology specialist, plans treatment to keep side effects as mild as possible. Practical strategies make a real difference for most patients.

• Slow titration: starting at the lowest dose and moving up only when you feel ready, or holding a step longer if needed
• Hydration: aiming for steady fluid intake through the day, since eating less often means drinking less too
• Protein first: building meals around protein to help protect muscle and reduce nausea from large carbohydrate or fatty meals
• Smaller, slower meals: stopping at the first sign of fullness rather than finishing the plate
• Fiber and movement to manage constipation, with medicine if required
• Medicine review: adjusting diabetes medicines and checking anything that slows digestion

Who should not use semaglutide

Semaglutide should not be used by people with a personal or family history of MTC or MEN2, during pregnancy, when trying to conceive (it is usually stopped at least two months beforehand), or while breastfeeding. Anyone with a previous serious allergic reaction to semaglutide should avoid it. People with a history of pancreatitis, gallbladder disease, severe gastroparesis, kidney disease or diabetic retinopathy need an individual assessment first.

If you are planning surgery or a procedure under sedation, tell the team you are using semaglutide, because delayed stomach emptying can affect anesthesia safety.

Red flags: when to seek urgent care

Call 119 or go to the nearest emergency room if you have any of the following while taking semaglutide. VEI Clinic does not provide emergency care, but we can refer you to a hospital and support your follow-up afterward.

• Severe abdominal pain, especially pain that spreads to your back
• Vomiting that will not stop, or being unable to keep fluids down
• Signs of dehydration: very dark urine, little urine, dizziness when standing
• Yellow skin or eyes, or upper right abdominal pain with fever
• Swelling of the face, lips or throat, or difficulty breathing
• Shakiness, sweating and confusion if you also take insulin or a sulfonylurea