Ozempic and Semaglutide Side Effects: The Label Data, Explained

Semaglutide has one of the most heavily documented safety profiles in modern pharmacology, and almost none of that documentation makes it into the average search result. What follows is the FDA prescribing information, quoted with its own numbers, its own placebo columns, and its own qualifiers. Where the label declines to give a number, this page declines too.

What Are the Side Effects of Ozempic?

The Ozempic prescribing information states that the most common adverse reactions reported in at least 5% of treated patients are nausea, vomiting, diarrhea, abdominal pain, and constipation. The numbers below come from the label's pooled placebo-controlled trials in adults with type 2 diabetes, reported as the percentage of patients in each arm.

Read the table as a whole rather than row by row. The label also reports the aggregate: gastrointestinal adverse reactions occurred in 15.3% of placebo patients, 32.7% of the 0.5 mg group, and 36.4% of the 1 mg group. In the separate trial comparing 1 mg with 2 mg, gastrointestinal reactions were reported in 34% of the 2 mg group versus 30.8% of the 1 mg group.

Beyond the at-least-5% list, the Ozempic label names lower-frequency gastrointestinal reactions including dyspepsia, eructation (belching), flatulence, and gastroesophageal reflux disease, each reported in under 5% of patients.

Semaglutide Side Effects by Product: Ozempic vs Wegovy vs Rybelsus

Semaglutide is one molecule sold under three brand names with three different FDA indications. Confusing them is the single most common error in consumer coverage, and it matters here because the reported side-effect frequencies are not the same.

Wegovy: the fullest side-effect list on any semaglutide label

Because Wegovy is studied at a higher maintenance dose in a larger non-diabetic population, its label carries the longest adverse-reaction table. In the pooled weight-reduction trials of Wegovy 2.4 mg injection (2,116 treated patients versus 1,261 on placebo), the label reports:

The two lines people never see quoted are the last three rows. Hair loss at 3% versus 1%, and dysesthesia (a grouped term covering paresthesia, burning sensation, and skin sensitivity) at 2% versus 1%, are on the label. So is fatigue at 11% versus 5%. Hair loss is quantified only here, on the Wegovy label. It is not absent from the other two: the Ozempic and Rybelsus labels list alopecia under Postmarketing Experience, in the skin and subcutaneous tissue category, where the label states frequency cannot be reliably estimated because the reports come from a population of uncertain size. Unquantified is not the same as unreported. If you want the same breakdown for the other major GLP-1, see our companion tirzepatide side effects guide, and for how the two molecules compare overall, our semaglutide vs tirzepatide comparison.

Rybelsus and the oral semaglutide tablets

Oral semaglutide is taken daily on an empty stomach with no more than four ounces of water, and the label instructs waiting at least 30 minutes before eating, drinking, or taking other oral medications. In the pooled placebo-controlled trials the label reports nausea in 11% of patients on 7 mg and 20% on 14 mg versus 6% on placebo, abdominal pain 10% and 11% versus 4%, diarrhea 9% and 10% versus 4%, decreased appetite 6% and 9% versus 1%, and vomiting 6% and 8% versus 3%. Overall gastrointestinal reactions were reported in 41% of the 14 mg group, 32% of the 7 mg group, and 21% of placebo patients.

The label is explicit that oral and injectable semaglutide are not substitutable on a milligram-to-milligram basis. If you are weighing a pill against a weekly injection, our GLP-1 pill guide covers the practical differences, and the Wegovy vs Ozempic comparison covers the two injectable semaglutide products side by side.

GLP-1 Side Effects: What the Whole Class Shares

Searching "GLP-1 side effects" instead of a brand name is the smarter query, because these drugs share a mechanism and therefore share a safety architecture. Every GLP-1 receptor agonist slows gastric emptying and acts on central appetite signaling, which is why the same cluster of complaints shows up on every label in the class.

The following warnings appear across the semaglutide, tirzepatide, liraglutide, and dulaglutide prescribing information:

• Gastrointestinal reactions. Nausea, vomiting, diarrhea, constipation, and abdominal pain dominate every label's common-reaction table, concentrated during dose escalation.
• Acute pancreatitis. Observed in patients treated with GLP-1 receptor agonists. The labels instruct discontinuation if pancreatitis is suspected.
• Acute gallbladder disease. Cholelithiasis and cholecystitis occur more often on drug than placebo.
• Hypoglycemia with insulin or insulin secretagogues. The GLP-1 itself rarely causes low blood sugar alone; combined with insulin or a sulfonylurea, the risk rises.
• Acute kidney injury from volume depletion. Postmarketing reports, some requiring hemodialysis, mostly in patients who became dehydrated from vomiting or diarrhea.
• Severe gastrointestinal adverse reactions. Reported postmarketing across the class; the Wegovy label states it is not recommended in patients with severe gastroparesis.
• Hypersensitivity reactions. Anaphylaxis and angioedema have been reported.
• Pulmonary aspiration during general anesthesia or deep sedation. Reported in patients on GLP-1 receptor agonists undergoing elective procedures. The labels instruct patients to tell their care team about any planned surgery or procedure.
• Boxed warning for thyroid C-cell tumors. Semaglutide, tirzepatide, liraglutide, and dulaglutide labels all carry it, and all are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.

Two warnings are semaglutide-specific rather than universal. The Ozempic and Rybelsus labels warn about diabetic retinopathy complications in patients with type 2 diabetes, and the Wegovy label carries the same warning for patients with type 2 diabetes taking it for weight reduction. The Wegovy label also warns about heart rate increase, reporting mean increases in resting heart rate of 1 to 4 beats per minute and noting that more treated than placebo patients had a maximum change of 20 bpm or more (26% versus 16%).

One more class-wide effect is not a "side effect" on any label but shows up in trial body-composition data: weight lost on a GLP-1 includes lean mass, not only fat. Our GLP-1 and muscle loss guide covers what the trials measured and what protects lean tissue. For the full roster of approved agents and how they differ, see the GLP-1 medications list.

Serious Warnings on the Semaglutide Label

The boxed warning

All three semaglutide labels open with the same boxed warning. In rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. The label states plainly 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. The label also notes that routine monitoring of serum calcitonin or thyroid ultrasound is of uncertain value for early detection.

The practical consequence is the contraindication: semaglutide is contraindicated in patients with a personal or family history of medullary thyroid carcinoma, in patients with Multiple Endocrine Neoplasia syndrome type 2, and in patients with a prior serious hypersensitivity reaction to semaglutide or any excipient.

Gallbladder disease

The Wegovy label reports cholelithiasis (gallstones) in 1.6% of injection-treated adults versus 0.7% of placebo patients, and 2.5% of tablet-treated versus 1% of placebo patients. Cholecystitis was reported in 0.6% versus 0.2%. The label specifically notes that the incidence was higher in treated patients aged 12 and older than in treated adults, with cholelithiasis reported in 3.8% of that pediatric group versus 0% on placebo.

Severe gastrointestinal reactions

"Severe" is a defined category on the label, not a figure of speech. In the adult weight-reduction trials, severe gastrointestinal adverse reactions were reported in 4.1% of Wegovy injection patients versus 0.9% on placebo, and in 2% of Wegovy tablet patients versus 0% on placebo.

Pregnancy

The Wegovy label states that weight loss offers no benefit to a pregnant patient and may cause fetal harm, and instructs discontinuation in pregnant patients using it for weight reduction. Novo Nordisk maintains a pregnancy exposure registry for patients exposed during pregnancy. Anyone who is pregnant, trying to conceive, or breastfeeding needs this conversation with a prescriber before starting or continuing.

Why Side Effects Cluster During Dose Escalation

The label answers this directly: the majority of reports of nausea, vomiting, and diarrhea occurred during dose escalation. That is the entire design logic behind the titration schedules. The following is what the FDA label specifies, reported here for education only. Your prescriber determines your dosing, and nothing on this page is a reason to start, change, skip, or combine doses.

Two label details are worth knowing because they explain unexpected symptom flare-ups. First, the labels state that the escalation steps exist specifically to reduce the risk of gastrointestinal reactions. Second, the Wegovy label instructs that if two or more consecutive doses are missed, escalation should be reinitiated at a lower dosage for the same reason. A gap in supply is a clinical event, not just an inconvenience. Our semaglutide dosing guide walks through the label schedules in more detail, and the tirzepatide dosing guide does the same for Mounjaro and Zepbound.

How Often People Stop Because of Side Effects

Discontinuation rate is the most honest single measure of tolerability, because it counts people who decided the trade was not worth it. The labels report:

• Ozempic. In the pooled placebo-controlled trials, 3.1% of the 0.5 mg group and 3.8% of the 1 mg group discontinued because of gastrointestinal adverse reactions, versus 0.4% on placebo.
• Wegovy 2.4 mg injection. 6.8% of treated patients and 3.2% of placebo patients permanently discontinued because of adverse reactions. The most common causes were nausea (1.8% versus 0.2%), vomiting (1.2% versus 0%), and diarrhea (0.7% versus 0.1%).
• Oral semaglutide. In a four-year cardiovascular outcomes trial, study drug was permanently discontinued because of an adverse event in 15.5% of tablet-treated patients versus 11.6% of placebo patients. Note the placebo rate: over four years, people stop trial drugs for many reasons.

The takeaway is that the overwhelming majority of people in these trials continued treatment. Common does not mean intolerable, and severe does not mean typical. What determines your experience is less the molecule than the clinical wrap around it: whether someone titrates you deliberately, monitors you, and adjusts when symptoms surface. That is worth weighing when you compare programs. Our guide to the best GLP-1 weight-loss programs compares what each program actually includes, and our weight-loss clinic directory lists cash-pay clinics by state.

Compounded Semaglutide Adds a Separate Risk

Everything above describes FDA-approved semaglutide products, whose safety data come from registration trials and whose manufacturing is FDA-inspected. Compounded semaglutide is not an FDA-approved product. The FDA does not review compounded drugs for safety, effectiveness, or quality before they reach patients.

The FDA has specifically alerted health care providers, compounders, and patients to dosing errors associated with compounded injectable semaglutide products, including reports of adverse events, some requiring hospitalization, that may be related to overdoses. The agency attributed errors to patients measuring and self-administering incorrect doses and to providers miscalculating doses, and pointed to two contributing factors: many patients receiving vials had no experience withdrawing medication from a vial into a syringe, and confusion between units of measurement (milliliters, milligrams, and "units") compounded the problem. Compounders also supply the product in different containers and at different concentrations.

Cost is usually the reason people land on a compounded product, and that is a real consideration rather than a foolish one. If price is what is driving the decision, compare the actual cash numbers first: our semaglutide cost guide, tirzepatide cost guide, and cheapest GLP-1 without insurance comparison use prices published by clinics and manufacturers rather than estimates. If semaglutide is not tolerable for you, our Ozempic alternatives guide covers what else is approved and what it costs.

When to Call a Clinician

The labels name specific scenarios where the instruction is to stop, seek care, or inform a provider. These are not judgment calls to make from a search result.

• Severe, persistent abdominal pain, with or without vomiting. The labels instruct discontinuation if pancreatitis is suspected.
• Vomiting or diarrhea you cannot keep ahead of. Dehydration is the documented path to acute kidney injury on these drugs.
• Right-upper-abdominal pain, fever, jaundice, or clay-colored stools. Possible gallbladder disease, which the label lists as a warning.
• Any planned surgery or procedure with anesthesia or deep sedation. Tell the surgeon and the anesthesiologist you take a GLP-1. Pulmonary aspiration has been reported.
• A neck lump, trouble swallowing, shortness of breath, or persistent hoarseness. These are the symptoms the boxed warning tells patients to report.
• Swelling of the face, lips, or tongue, rash, or trouble breathing. Serious hypersensitivity reactions including anaphylaxis and angioedema have been reported.
• Vision changes, particularly if you have type 2 diabetes and a history of retinopathy.
• Repeated low blood sugar, especially if you also take insulin or a sulfonylurea.
• Pregnancy, or planning one. The label instructs discontinuation in pregnant patients using semaglutide for weight reduction.