Nausea is the side effect most people get, and the FDA label puts a number on it: 15.8% of patients at the 0.5 mg dose and 20.3% at 1 mg, compared with 6.1% on placebo. Vomiting, diarrhea, abdominal pain, and constipation are the other reactions the label reports in at least 5% of patients. Almost all of it is digestive, almost all of it is mild to moderate, and most of it clusters around the weeks when the dose is going up.
That is the honest headline. But "Ozempic side effects" covers three things that get mashed together online: the common stomach complaints, a short list of rarer risks serious enough to print in the label, and a vision signal regulators outside the United States have acted on while the FDA so far has not. They deserve separating, because the odds attached to them are nothing alike.
These are the reactions occurring in 5% or more of patients in the pooled placebo-controlled type 2 diabetes trials, as reported in the Ozempic prescribing information:
| Side effect | Placebo | 0.5 mg | 1 mg | |---|---|---|---| | Nausea | 6.1% | 15.8% | 20.3% | | Vomiting | 2.3% | 5.0% | 9.2% | | Diarrhea | 1.9% | 8.5% | 8.8% | | Abdominal pain | 4.6% | 7.3% | 5.7% | | Constipation | 1.5% | 5.0% | 3.1% |
A few things worth reading off that table. Nausea and vomiting scale clearly with dose. Abdominal pain and constipation do not, and at 1 mg both are reported at rates close to or below placebo, which is a good reminder that not every symptom someone experiences on this drug is caused by the drug.
Below the 5% threshold, the label notes fatigue and dysgeusia (a metallic or altered taste) at frequencies above 0.4%. Injection site reactions such as discomfort and redness were reported in just 0.2% of Ozempic-treated patients, which surprises people who assume a weekly injection means weekly skin trouble. The label also records a mean heart rate increase of 2 to 3 beats per minute.
For the 2 mg dose, the label's head-to-head comparison reported gastrointestinal adverse reactions in 34% of patients on 2 mg versus 30.8% on 1 mg. The step from 1 mg to 2 mg is a smaller tolerability jump than the step from starting the drug at all.
The number that matters most is how many people actually quit. Discontinuation due to gastrointestinal reactions was 3.1% at 0.5 mg and 3.8% at 1 mg, against 0.4% on placebo. So roughly 96 out of 100 people who start these doses do not stop because of their stomach.
Search this topic and you will find nausea rates near 44%. Those are real numbers, but they are not Ozempic numbers. They come from the STEP obesity trials of semaglutide 2.4 mg, sold as Wegovy. Same molecule, higher dose, different trial population.
In a pooled analysis of STEP 1 through 3, nausea was reported by 43.9% of participants on semaglutide 2.4 mg versus 16.1% on placebo, with vomiting at 24.5%, diarrhea at 29.7%, and constipation at 24.2%. Ozempic tops out at 2 mg. If you are comparing your experience to a statistic, check which dose produced it. Our Ozempic vs Wegovy comparison breaks down where the two diverge.
This is the question the percentages never answer, and it is the one most people actually want.
The best published data on duration comes from that same semaglutide 2.4 mg analysis, which tracked individual episodes rather than just whether a symptom ever occurred. A single episode of nausea lasted a median of 8 days. Vomiting episodes ran a median of 2 days, diarrhea a median of 3 days. Across all gastrointestinal events, 98.1% were mild or moderate in intensity, and 4.3% of participants discontinued because of them, with most of those discontinuations happening during dose escalation.
The timing pattern is the useful part: events clustered during and shortly after each dose increase, and the cumulative share of participants experiencing their first gastrointestinal event plateaued after roughly week 20. In plain terms, the symptoms tend to arrive in waves tied to dose changes rather than building steadily forever, and for most people the drug stops introducing new problems after the first several months.
Two honest caveats. This duration data is from the 2.4 mg obesity trials, and no equivalent episode-duration analysis has been published for the 0.5, 1, and 2 mg doses. And gradual escalation is standard precisely because it reduces these symptoms, but how fast you climb, whether you hold, and whether you step back down are decisions for your prescriber. Our Ozempic starting guide covers what the escalation schedule looks like, and if nausea is your main obstacle, nausea-friendly meals and our deep dive on semaglutide nausea go further than this page can.
Ozempic carries a boxed warning, the FDA's most serious label warning. In rodents, semaglutide caused dose-dependent and duration-dependent thyroid C-cell tumors at clinically relevant exposures. Whether it causes thyroid C-cell tumors, including medullary thyroid carcinoma, in humans is unknown, because the human relevance of the rodent finding has not been determined. That uncertainty is why the drug is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome, alongside serious hypersensitivity to semaglutide. See who should not take a GLP-1 for the full picture.
Beyond the boxed warning, the label's warnings and precautions section covers ten items: thyroid C-cell tumors, acute pancreatitis, diabetic retinopathy complications, never sharing a pen between patients, hypoglycemia when combined with insulin or insulin secretagogues, acute kidney injury from volume depletion, severe gastrointestinal reactions, hypersensitivity reactions, acute gallbladder disease, and pulmonary aspiration during general anesthesia or deep sedation.
Some of these carry numbers. Pancreatitis occurred at 0.3 cases per 100 patient-years on Ozempic versus 0.2 on comparators. Cholelithiasis (gallstones) was reported in 1.5% and 0.4% of patients on 0.5 mg and 1 mg respectively, with none in placebo. The acute kidney injury reports are postmarketing, mostly in people who became dehydrated from severe nausea, vomiting, or diarrhea, which is the practical reason hydration matters more on this drug than off it. The label states Ozempic is not recommended in patients with severe gastroparesis, and ileus appears in postmarketing experience. The aspiration warning reflects rare reports of patients having residual stomach contents before anesthesia despite following fasting instructions, so surgical and procedural teams need to know you are on it.
Diabetic retinopathy deserves its own note because the evidence is specific. In SUSTAIN-6, retinopathy complications occurred in 3.0% of semaglutide patients versus 1.8% on placebo (hazard ratio 1.76, 95% CI 1.11 to 2.78). Critically, 83.5% of the patients who had these complications already had retinopathy at baseline, and among that subgroup the rates were 8.2% versus 5.2%. This is largely a risk concentrated in people who already have eye disease and whose blood sugar drops quickly, not a general warning for everyone.
In June 2025, the European Medicines Agency's safety committee concluded its review and determined that non-arteritic anterior ischemic optic neuropathy (NAION), a form of sudden vision loss from reduced blood flow to the optic nerve, is a very rare side effect of semaglutide, meaning it may affect up to 1 in 10,000 users. The EMA required it be added to product information for Ozempic, Wegovy, and Rybelsus. The WHO issued its own statement the same month.
The United States label is where this gets awkward. As of the revision reviewed for this article, NAION does not appear in the FDA's Ozempic label, and other regulators including Australia's TGA have moved to add it while the FDA has not. We are naming that divergence rather than resolving it, because it is not resolved. What can be said fairly: the association has been reported in multiple observational studies since 2024, causality is not established, and even by the EMA's own classification the absolute risk is very rare. Sudden vision loss or rapidly worsening eyesight is a contact-your-doctor-today symptom regardless of what any label says. See GLP-1 vision changes for more.
Plenty of commonly discussed effects are not label adverse reactions. Hair loss is widely reported but generally attributed to telogen effluvium from rapid weight loss rather than a direct drug effect. Lean mass loss accompanies any substantial weight loss, and the semaglutide body composition data comes from the higher-dose obesity trials. Mood changes have been investigated without a confirmed causal link. Track these without assuming the drug is the cause.
Call promptly for severe or persistent abdominal pain, especially radiating to the back and with vomiting (possible pancreatitis); signs of dehydration or a drop in urine output; sudden vision changes; symptoms of a serious allergic reaction; or a neck lump, hoarseness, or trouble swallowing. Tell any surgeon or anesthesiologist that you take Ozempic before a procedure. And if nausea is stopping you from keeping fluids down, that is a dose conversation, not something to push through.
What is the most common side effect of Ozempic? Nausea, reported in 15.8% of patients at 0.5 mg and 20.3% at 1 mg versus 6.1% on placebo in the label's pooled trials.
Do Ozempic side effects go away? For most people they ease. Gastrointestinal events cluster around dose increases, individual nausea episodes ran a median of 8 days in the semaglutide 2.4 mg analysis, and the rate of people experiencing a first event plateaued after about week 20. Some people have symptoms that persist and need a dose change.
How many people stop Ozempic because of side effects? In the trials, 3.1% at 0.5 mg and 3.8% at 1 mg discontinued due to gastrointestinal reactions, versus 0.4% on placebo.
Does Ozempic cause thyroid cancer? Unknown in humans. The boxed warning reflects thyroid C-cell tumors in rodents, and the human relevance has not been determined. It is contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
Can Ozempic cause blindness? The EMA classified NAION as a very rare side effect in 2025, affecting up to 1 in 10,000 users, and required a label update in Europe. The US label had not added it as of the version reviewed here. Separately, the label warns about diabetic retinopathy complications, a risk concentrated in people who already have retinopathy. Report sudden vision changes immediately.
This article describes what published trials and regulatory labels report. It is not medical advice, and dosing decisions belong to your prescriber.