Tirzepatide label added ileus in July 2023, two months before semaglutide

The prescribing information for Mounjaro (tirzepatide) was updated in July 2023 to add ileus to the list of reported adverse reactions. The Ozempic (semaglutide) label gained the same entry in September 2023, two months later ^[1].

Both additions came from postmarketing reports — side effects reported by patients and clinicians after a drug is approved and in wider use — rather than from data collected in clinical trials. That is why the Mounjaro label states that a frequency for ileus cannot be reliably estimated. The label does not disclose how many cases were reported, when the first report arrived, or how regulators evaluated them ^[1].

Ileus is a condition in which the intestines stop moving their contents through normally. It can produce a backup similar to a blockage even when nothing is physically obstructing the bowel.

The Mounjaro label's warnings section says use of the drug "has been associated with gastrointestinal adverse reactions, sometimes severe," and that Mounjaro is not recommended in patients with severe gastroparesis, a condition in which the stomach empties unusually slowly. The label also notes that tirzepatide delays gastric emptying, which can affect how oral medicines are absorbed ^[1].

The same labeling document carries a boxed warning about thyroid C-cell tumors seen in rats, with the note that it is unknown whether Mounjaro causes such tumors, including medullary thyroid carcinoma, in humans. Mounjaro is contraindicated in people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2 ^[1].

The most common adverse reactions, reported in at least 5 percent of patients treated with Mounjaro, are nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia and abdominal pain ^[1].

Mounjaro received its initial U.S. approval in 2022. It is indicated to improve blood sugar control in adults and in children 10 years and older with type 2 diabetes, and to reduce the risk of major adverse cardiovascular events — cardiovascular death, non-fatal heart attack or non-fatal stroke — in adults with type 2 diabetes who are at high risk for those events ^[1].

Why it matters for patients

A drug label is the reference clinicians and pharmacists use when they weigh whether a symptom is worth acting on. Listing ileus means the reports were serious enough to be recorded in that document, and it gives a prescriber a documented reason to take severe or persistent stomach and bowel symptoms seriously ^[1].

It does not mean the reaction is common. Because the entries rest on voluntary reports rather than a controlled trial, the label offers no rate — readers cannot conclude from it whether ileus happens in one in a thousand patients or far fewer. That uncertainty is stated in the label itself ^[1].

Digestive complaints already dominate the label's list of common side effects. The warnings direct providers to stop the drug if pancreatitis is suspected, to monitor kidney function in patients whose reactions could lead to fluid loss, and to avoid Mounjaro in patients with severe gastroparesis ^[1].

A labeling change is not a recall. Mounjaro remains an approved product marketed under a new drug application, and the label continues to be revised as new information is reviewed ^[1].

What happens next

The current Mounjaro label, revised in August 2026, lists several recent major changes: a pediatric indication for patients 10 years and older in December 2025, an update to the severe gastrointestinal adverse reactions warning in December 2025, a KwikPen-sharing warning in January 2026, and changes covering major adverse cardiovascular events and diabetic retinopathy complications in August 2026 ^[1]. The label gives no timeline for a frequency estimate for ileus or for any further gastrointestinal warning ^[1].