GLP-1 side effects: how common they are, how long they last and which are serious

The table puts the two labels side by side. The Wegovy column is the 2.4 mg weekly dose; the Zepbound column gives the range across its 5, 10 and 15 mg maintenance doses. Each figure is the share of people who reported the effect at any point in trials that ran 68 to 72 weeks.

Sources: Wegovy label Table 3 ^[1]; Zepbound label Table 1 ^[2]. Zepbound also lists injection-site reactions, in 6% to 8% against 2% ^[2].

Two cautions in reading it. The labels themselves say rates from different drugs' trials cannot be compared directly, because the trials differed ^[1][2]. And a "yes" in a trial means the effect happened at least once, not that it lasted the whole time.

Wegovy tablets, taken daily, produced the same kinds of side effects at similar rates in their trial ^[1]. The new 7.2 mg Wegovy dose added more of them: 39% nausea, 22% vomiting and, unusually, 22% dysesthesia, a burning or tingling feeling on the skin, against 6% on 2.4 mg ^[1].

Both drugs slow the stomach and act on appetite centers in the brain, so the stomach effects come with the mechanism. They are worst when the dose goes up. That is the stated reason for the escalation schedules: Wegovy starts at 0.25 mg and Zepbound at 2.5 mg, and neither starting dose is meant to be the long-term one ^[1][2].

Most people stay on treatment. In the Wegovy trials, 6.8% stopped because of side effects, against 3.2% on placebo; nausea, vomiting and diarrhea were the main reasons ^[1]. In the Zepbound trials it was 4.8% to 6.7% by dose, against 3.4%, and most of those stopped in the first few months ^[2].

These are the warnings both labels carry, in plain terms ^[1][2]:

• Thyroid C-cell tumors. A boxed warning. Both drugs caused these tumors in rodents; whether they do in people is not known. Neither drug is for anyone with a personal or family history of medullary thyroid cancer or MEN 2.
• Pancreatitis. Severe stomach pain that will not go away, sometimes spreading to the back, is a reason to stop and call a doctor. Since approval, necrotizing and fatal cases have been reported ^[1][2].
• Gallbladder disease. Gallstones and inflammation, which can need surgery. Fast weight loss raises the risk, but the Wegovy label notes it was more common than on placebo even after allowing for weight lost ^[1].
• Kidney injury from dehydration. Vomiting and diarrhea can dry you out enough to hurt the kidneys. Since approval, some Zepbound cases have needed dialysis ^[2].
• Severe stomach problems. Including, since approval, bowel obstruction, ileus and fecal impaction ^[1][2].
• Low blood sugar. Mainly in people who also take insulin or a sulfonylurea.
• Allergic reactions. Including anaphylaxis and swelling of the face or throat.
• Diabetic eye disease. People with type 2 diabetes and retinopathy should be watched, because fast drops in blood sugar can worsen it.
• Food in the lungs under anesthesia. Because the stomach empties slowly, tell anyone sedating you that you take one of these drugs.
• Heart rate. Wegovy can raise resting heart rate ^[1].

One warning has gone. The Wegovy label carried a section on suicidal behavior and ideation; it was removed in February 2026 ^[1].

A large health-record study of people with type 2 diabetes compared the severe stomach outcomes (pancreatitis, gallbladder disease, bowel obstruction, gastroparesis and severe constipation) across semaglutide, tirzepatide and the older dulaglutide. The risk was about the same for all three ^[5].

Hair loss is on both labels. In the Zepbound trials it was 4% to 5% against 1% on placebo, and the label ties it to weight loss: it was reported by 7.1% of women and 0.5% of men, and nobody stopped Zepbound because of it ^[2]. On Wegovy it was 3% at 2.4 mg and 6% at 7.2 mg ^[1].

Studies outside the label point the same way. A 2026 meta-analysis of nine trials with 4,114 GLP-1 users found hair loss about three times as often as on placebo, with an overall rate of 3.9% ^[3]. In a health-record study of people with type 2 diabetes, starting a GLP-1 drug carried a higher risk of new hair loss than starting an SGLT-2 or DPP-4 drug, though the absolute risk was low ^[4]. The increase was in non-scarring hair loss.

Neither label has a warning about alcohol. What exists is research on whether these drugs reduce drinking.

Three randomized trials have tested semaglutide in alcohol use disorder:

• 48 adults on low weekly doses for nine weeks drank less in a supervised lab session and had fewer drinks on the days they drank, but no fewer drinks per day overall ^[7].
• 108 adults with obesity on 2.4 mg weekly for 26 weeks cut their heavy drinking days by 13.7 percentage points more than placebo ^[8].
• 50 adults on oral semaglutide for eight weeks had fewer heavy drinking days, with no change in drinks per day ^[9].

None of this is an approved use. In practice, the overlap that matters is dehydration: alcohol on top of vomiting or diarrhea adds to the kidney risk in § 03, and in people taking insulin or a sulfonylurea, both alcohol and the drug can lower blood sugar.

Reports have linked semaglutide to NAION, a sudden loss of vision from poor blood flow to the optic nerve. It is not among the warnings on the US labels for Wegovy or Ozempic ^[1]. A 2026 meta-analysis of six observational studies covering 4.8 million people did not find a consistent overall increase. The certainty was low: the risk looked raised in type 2 diabetes and not in obesity, and the authors could not separate the drug from the disease ^[6]. Sudden vision loss on any drug needs urgent care.

For the approved drugs, the side effects are known in unusual detail because tens of thousands of people took them in trials. Most are stomach effects that are worst early. The serious ones are uncommon, and most have warning signs: lasting stomach pain, signs of dehydration, swelling of the face or throat.

That knowledge belongs to the approved products. A compounded or sublingual version uses the same molecule but has not been through those trials, and its dose depends on the pharmacy that made it. What the drugs do for weight, and how they compare, is on our pages for semaglutide, tirzepatide and the GLP-1 class.