Semaglutide Side Effects
Semaglutide is the active ingredient in two well known once weekly injections: Ozempic, approved for type 2 diabetes, and Wegovy, approved for weight management. Because the ingredient is the same, the side effect profile is shared. This page explains that shared profile from the two FDA approved labels, and where the brand pages go deeper. It is education only, not medical advice.
One ingredient, two brands
Ozempic and Wegovy are not two different medicines that happen to work alike. They are the same drug, semaglutide, sold under two names for two different uses, with two different dosing schedules. The semaglutide dosage chart puts both schedules side by side. Each brand also has its own detailed guide on this site: Ozempic side effects and Wegovy side effects.
The shared side effect profile
Across both labels, the reactions reported most often are gastrointestinal, which fits how semaglutide works: it slows stomach emptying and reduces appetite. The shared core list is:
- Nausea. The most frequently reported reaction on both labels.
- Diarrhea and vomiting. Reported most often while the dose is being increased.
- Constipation. A natural counterpart to slower digestion.
- Stomach pain. Abdominal pain or discomfort.
- Reduced appetite. Part of how the medicine works, and itself a listed reaction.
- Indigestion and reflux. Dyspepsia, belching, gas and gastroesophageal reflux appear on the labels.
Headache, fatigue and dizziness also appear, and hair loss is listed among the reactions reported in the Wegovy trials. Shedding on these medicines is usually tied to rapid weight loss itself, as our GLP-1 hair loss guide explains.
Why the two labels read a little differently
If you compare the Ozempic and Wegovy labels side by side, the lists are close but not identical. That is because the brands were studied in different groups of people: the Ozempic trials were in people with type 2 diabetes, at doses up to 2 mg, while the Wegovy trials were in people with overweight or obesity, at doses up to 2.4 mg. Different study populations and different doses surface slightly different reactions, and each label also carries warnings that matter most for its own use, such as the low blood sugar discussion on the diabetes label. The underlying profile of the ingredient is the same.
Warnings that appear on the semaglutide labels
Boxed warning: thyroid C-cell tumors. Both labels carry the strongest FDA warning, about a possible risk of thyroid C-cell tumors. In animal studies, semaglutide caused these tumors in rodents. It is not known whether it causes them in people. The labels say the medicines should not be used by people with a personal or family history of medullary thyroid carcinoma, or with multiple endocrine neoplasia syndrome type 2.
Pancreatitis. Inflammation of the pancreas has been reported. Severe stomach pain, sometimes spreading to the back, is the warning sign the labels describe.
Gallbladder problems. Gallstones and gallbladder inflammation have been reported, and rapid weight loss itself raises gallstone risk.
Severe stomach problems. Because semaglutide slows stomach emptying, the labels state the medicines are not recommended for people with severe gastroparesis.
Diabetic retinopathy complications. The labels carry a warning for people with diabetic retinopathy, and advise reporting any vision changes.
Allergic reactions. Serious allergic reactions, including anaphylaxis and swelling of the face, lips or tongue, have been reported.
When to get medical care promptly
Whichever brand is used, some symptoms should never be waited out. Seek medical care promptly for severe or persistent stomach pain, signs of an allergic reaction such as swelling of the face, lips or tongue or trouble breathing, yellowing of the skin or eyes, or a lump or swelling in the neck, a hoarse voice, or trouble swallowing. Ongoing vomiting or diarrhea that stops you drinking enough fluid also deserves a prompt call, because dehydration can strain the kidneys.
Frequently asked questions
Are Ozempic and Wegovy the same drug?
They contain the same active ingredient, semaglutide. Ozempic is approved for type 2 diabetes and Wegovy for weight management. Each brand has its own dosing schedule and its own label, but the ingredient, and the way it works in the body, are the same.
Are semaglutide side effects the same for both brands?
Largely, yes. Both labels name the same core group of reactions: nausea, vomiting, diarrhea, constipation, stomach pain and reduced appetite, along with indigestion and reflux. The wording and emphasis differ a little because the brands were studied in different groups of people, at different doses, for different conditions.
What are the most common semaglutide side effects?
Across both labels, the most commonly reported reactions are gastrointestinal: nausea, diarrhea, vomiting, constipation and stomach pain, plus reduced appetite. Headache, fatigue and dizziness also appear, and hair loss is listed on the Wegovy label. These effects are reported most often while the dose is being increased.
Does semaglutide affect the eyes?
The semaglutide labels carry a warning about complications of diabetic retinopathy, a diabetes related eye condition. In a trial in people with type 2 diabetes, these complications were reported more often in those taking semaglutide. The labels advise people with a history of diabetic retinopathy to tell their prescriber and to report any vision changes.
What is the boxed warning for semaglutide?
Both the Ozempic and Wegovy labels carry a boxed warning about thyroid C-cell tumors. In studies, semaglutide caused these tumors in rodents. It is not known whether it causes them in people. The labels say the medicines should not be used by people with a personal or family history of medullary thyroid carcinoma, or with multiple endocrine neoplasia syndrome type 2.