Ozempic Side Effects, From Tiredness and Hair Loss to the Boxed Warning

The most common Ozempic side effects are nausea, vomiting, diarrhea, abdominal pain and constipation, each reported in at least 5% of patients.1 In the Ozempic placebo-controlled trials, nausea affected 15.8% of patients on 0.5 mg and 20.3% on 1 mg, against 6.1% on placebo.1

At Wegovy's higher 2.4 mg dose the rates are higher: in the weight-management trials, 44% of patients reported nausea, 30% diarrhea, 24% vomiting and 24% constipation, against 16%, 16%, 6% and 11% on placebo.2

Yes, it can. Fatigue is a listed side effect of both Ozempic and Wegovy, and it is more common at the higher weight-loss doses. The Ozempic label lists fatigue among adverse reactions reported in more than 0.4% of patients.1

Yes. In the Wegovy 2.4 mg trials for weight loss, 11% of patients reported fatigue or weakness (asthenia), compared with 5% on placebo.2 Dizziness was reported by 8%, against 4% on placebo.2

The label does not single out one cause. Other reactions on the same list — vomiting, diarrhea, low blood sugar in people with type 2 diabetes — can all leave people drained, and the Wegovy label notes that hypoglycemia occurred in 6% of patients with type 2 diabetes on 2.4 mg versus 2% on placebo.2 Persistent or severe tiredness is worth raising with a prescriber.

Yes. Constipation was reported by 5% of patients on Ozempic 0.5 mg and 3.1% on 1 mg, against 1.5% on placebo, and by 24% of patients on Wegovy 2.4 mg against 11% on placebo.1,2 Since approval, there have also been reports of ileus, intestinal obstruction and severe constipation including fecal impaction.1

Burping is a recognized side effect: the labels list it as "eructation." It was reported by 2.7% of patients on Ozempic 0.5 mg and 1.1% on 1 mg, against 0% on placebo, and by 7% on Wegovy 2.4 mg against under 1% on placebo.1,2 Indigestion, gas and reflux appear on the same lists.1,2 The labels do not describe the smell; "sulfur burps" is a patient term.

Semaglutide slows how quickly the stomach empties, which is the mechanism the labels tie to its effects on digestion.1,2

Hair loss is a listed side effect of Wegovy, and the label links it to weight reduction. In pooled trials, 3.3% of patients on Wegovy 2.4 mg reported hair loss (4% of women, 0.9% of men), against 1% on placebo.2 At the 7.2 mg dose, 5.8% reported it (8.4% of women).2 For Ozempic, alopecia appears among reactions reported after approval.1

For most people, the digestive side effects are temporary and concentrated in the dose-escalation weeks. The Ozempic label says most reports of nausea, vomiting and diarrhea occurred during dose escalation.1 In the STEP 1 trial, nausea and diarrhea were typically transient, mild to moderate, and subsided with time.3

That is why both drugs start at 0.25 mg and step up every 4 weeks.1,2 The Wegovy label allows a prescriber to delay the next step by 4 weeks if a dose is not tolerated.2 Some people do stop: 3.1% of patients on Ozempic 0.5 mg and 3.8% on 1 mg discontinued because of gastrointestinal effects, against 0.4% on placebo.1

It is not known. Semaglutide causes thyroid C-cell tumors in rodents, and whether it causes them — including medullary thyroid carcinoma (MTC) — in humans has not been determined, which is why both labels carry a boxed warning.1,2

The labels say the reports of MTC in patients taking liraglutide, another GLP-1 drug, are insufficient to establish or exclude a causal link.1 Ozempic and Wegovy must not be used by people with a personal or family history of MTC or with multiple endocrine neoplasia syndrome type 2 (MEN 2).1,2 Symptoms to report include a lump in the neck, trouble swallowing, shortness of breath and persistent hoarseness.1

Beyond the boxed warning, the current labels list these warnings and precautions:1,2

• Acute pancreatitis, including fatal cases. Persistent, severe abdominal pain, sometimes spreading to the back, is the signal to stop and seek care.1
• Gallbladder disease. In Ozempic trials, gallstones were reported in 1.5% of patients on 0.5 mg and 0.4% on 1 mg, and in no placebo patients.1
• Low blood sugar when combined with insulin or a sulfonylurea; the dose of those drugs may need to come down.1
• Acute kidney injury, mostly in people who became dehydrated from nausea, vomiting or diarrhea, sometimes requiring dialysis.1
• Severe gastrointestinal reactions; neither drug is recommended for people with severe gastroparesis.1,2
• Serious allergic reactions, including anaphylaxis and angioedema.1
• Diabetic retinopathy complications. In a 2-year trial, they occurred in 3.0% of Ozempic patients versus 1.8% on placebo, with a larger difference in those with existing retinopathy.1
• Pulmonary aspiration under anesthesia or deep sedation, because food can remain in the stomach; tell your care team about any planned procedure.1
• Faster heart rate, a Wegovy warning: resting heart rate rose by 1 to 4 beats per minute on average.2

The Ozempic Medication Guide asks patients to report any change in vision.1 The current U.S. labels (revised May and June 2026) do not list non-arteritic anterior ischemic optic neuropathy (NAION) among their warnings.1,2 Our safety page keeps these warnings in one place.

"Ozempic face" — sunken cheeks, new wrinkles and loose skin — comes from rapid loss of facial fat, not from the drug itself, so the main lever is the pace of weight loss.6 Cleveland Clinic suggests aiming for 1 to 2 pounds a week, eating enough protein, staying hydrated, keeping up skincare and using sunscreen daily.6

Semaglutide leaves the body slowly, and weight tends to return. With a half-life of about one week, it stays in circulation for about 5 weeks after the last Ozempic dose, and about 5 to 7 weeks after Wegovy 2.4 mg, 7.2 mg or the 25 mg tablet.1,2

In the STEP 1 extension, people who stopped semaglutide 2.4 mg after 68 weeks regained two-thirds of their prior weight loss within a year, and most cardiometabolic improvements drifted back toward baseline.4 For people with type 2 diabetes, stopping also removes a glucose-lowering medicine, so it is a decision to plan with a prescriber. Restarting Wegovy after two or more missed doses means re-escalating from a lower dose.2

Response varies, and the dose, the time on treatment and whether you have type 2 diabetes all change it. In STEP 1, 86.4% of adults without diabetes on semaglutide 2.4 mg lost at least 5% of body weight by week 68 — meaning about 1 in 7 did not.3

• Diabetes. In STEP 2, adults with type 2 diabetes on 2.4 mg lost a mean 9.6% over 68 weeks, compared with 14.9% for adults without diabetes in STEP 1.5,3
• Dose. Ozempic's maximum is 2 mg weekly; Wegovy's usual maintenance dose is 2.4 mg, and adults who tolerate 2.4 mg for at least 4 weeks may go up to 7.2 mg when more weight reduction is clinically indicated.1,2
• Time. The Wegovy injection schedule takes 16 weeks to reach the maintenance dose, and steady drug levels take 4 to 5 weeks at any dose.2,1
• Missed doses. Two or more missed Wegovy doses in a row mean restarting at a lower dose.2 Our missed-dose tool applies the rules.

Both labels describe semaglutide as an addition to diet and physical activity, not a replacement.1,2 If progress stalls, a prescriber can review the dose, the brand and alternatives such as tirzepatide; see Mounjaro vs Ozempic and tirzepatide vs semaglutide.

Are Ozempic and Wegovy side effects the same? The same drug carries the same warnings, but Wegovy's higher doses bring higher rates of most digestive side effects.1,2 Ozempic vs Wegovy compares them.

Does compounded semaglutide have different side effects? Compounded products are not FDA approved, so they have no reviewed label of their own. See compounded semaglutide vs Ozempic.

Can injection technique cause side effects? Technique affects whether you get your full dose; the instructions warn that removing the pen too early can leave part of it undelivered.1 See how to inject Ozempic.

When should I get urgent help? The Ozempic label names severe, persistent abdominal pain (a possible sign of pancreatitis) and serious allergic reactions as reasons to stop the drug and seek medical care, and asks prescribers to watch kidney function in patients who become dehydrated from vomiting or diarrhea.1

If side effects or cost are shaping your choice of medicine, compare doses and prices on Ozempic cost and Wegovy cost, and start with what is Ozempic for the basics.

This article is for information only and is not medical advice. Ozempic and Wegovy are prescription drugs with real risks and side effects — talk to a licensed clinician before starting, changing or stopping any treatment.