Semaglutide Side Effects (What the FDA Label Lists)

By DoseGauge Editorial · Updated 2026-06-12 · 5 min read

According to the FDA labels for semaglutide (Ozempic and Wegovy), the most common side effects are gastrointestinal: nausea, diarrhea, vomiting, constipation, and abdominal pain. Both labels carry a boxed warning about thyroid C-cell tumors observed in rodents, a contraindication tied to certain thyroid cancer history, and several other warnings. Everything below is taken from those labels. It is information, not medical advice, and it is not a complete list of every reaction in the label.

Common side effects

The semaglutide labels list gastrointestinal reactions as the most common. The Ozempic label names the following among reactions reported in at least 5% of patients:

• Nausea
• Vomiting
• Diarrhea
• Abdominal pain
• Constipation

The Wegovy label lists those same gastrointestinal reactions and adds others among its common adverse reactions, including headache, fatigue, dyspepsia, dizziness, abdominal distension, eructation, flatulence, gastroenteritis, gastroesophageal reflux disease, and nasopharyngitis. Both labels note that gastrointestinal reactions occurred more frequently during dose escalation.

This list has two limits. First, it is the common-frequency tier (reactions at or above the labels' reporting threshold), not the full catalog. The labels' adverse-reaction tables contain additional, less frequent reactions. Second, the list is descriptive: it records what was reported, at what rate, in the studied populations. It does not predict whether a given person will have any of these reactions.

Serious warnings and the boxed warning

Both labels open with a boxed warning, the FDA's most prominent warning format. Its substance: in rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors, and it is unknown whether semaglutide causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, because the human relevance of the rodent finding has not been determined.

Tied to that warning, both labels list two contraindications:

• A personal or family history of medullary thyroid carcinoma (MTC), or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
• A known hypersensitivity to semaglutide or any of the product components.

Other warnings and precautions

The labels' Warnings and Precautions sections cover several distinct risks. Each is attributed to the label, not to any judgment on this page:

• Acute pancreatitis. Pancreatitis has been reported in patients treated with semaglutide.
• Acute gallbladder disease. Events such as cholelithiasis and cholecystitis have been reported.
• Hypoglycemia. The risk of low blood sugar rises when semaglutide is combined with an insulin secretagogue or insulin.
• Acute kidney injury. Gastrointestinal effects can cause dehydration, which the label links to kidney injury.
• Diabetic retinopathy complications in patients with a history of diabetic retinopathy.
• Hypersensitivity reactions. Serious reactions have been reported.
• Suicidal behavior and ideation. The Wegovy label states that patients should be monitored for the emergence or worsening of depression, suicidal thoughts, or behavior.

The Wegovy label additionally notes a heart rate increase among its warnings. These reflect the section headings in the labels. The labels themselves contain the full detail and the complete adverse-reaction tables.

The labels tier these risks. The boxed warning sits at the top and addresses the thyroid C-cell tumor finding. Contraindications come next and define who should not receive the drug at all. Warnings and precautions then describe risks that call for monitoring or caution during use. The common gastrointestinal reactions sit lower because they are frequent but generally milder than the items above them.

What this means for dosing

The labeled titration schedule, starting at 0.25 mg once weekly and stepping up at intervals of at least 4 weeks, is structured to reach a maintenance dose while managing the gastrointestinal reactions that cluster around dose increases. That is the label's stated rationale for stepping up gradually rather than starting high. It is the reasoning behind the schedule, not a suggestion about what you should do.

If you are converting a labeled dose into syringe units from a reconstituted vial, the calculator does that arithmetic from your inputs. It computes; it does not advise.

Frequently asked questions

Do semaglutide side effects go away?

The labels state that gastrointestinal reactions were most common during dose escalation. They do not promise that any individual's side effects resolve or persist. How side effects behave over time for a specific person is a clinical question for a prescriber.

What are the most common semaglutide side effects?

Per the labels, the most common adverse reactions are gastrointestinal: nausea, diarrhea, vomiting, constipation, and abdominal pain. The Wegovy label lists additional common reactions such as headache, fatigue, and dyspepsia.

Who should not take semaglutide?

The labels contraindicate it in people with a personal or family history of medullary thyroid carcinoma or MEN 2, and in people with a known hypersensitivity to semaglutide or its components. Eligibility beyond those contraindications is determined by a clinician.

Is the boxed warning based on human cancer cases?

No. The boxed warning is based on thyroid C-cell tumors observed in rodents. The labels state that it is unknown whether semaglutide causes thyroid C-cell tumors, including medullary thyroid carcinoma, in humans, because the human relevance of the rodent finding has not been determined.

Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.