Judge weighs expert testimony on whether GLP-1 drugs cause gastroparesis

A federal judge in Philadelphia is weighing whether scientific experts may testify that Ozempic, Wegovy, Mounjaro and other GLP-1 drugs can cause gastroparesis, a condition in which the stomach empties too slowly. The hearing on expert admissibility is the central event in the consolidated federal litigation, known as MDL 3094, which covers gastrointestinal injury claims against the drugs' makers ^[1][2].

The MDL was created in February 2024 and is before Judge Karen S. Marston in the Eastern District of Pennsylvania ^[1]. As of September 2026, 4,022 cases were pending out of 4,056 filed, a 202% increase since January 2025 ^[1]. About 75% of the complaints allege gastroparesis, 18% allege ileus and 8% allege gallbladder injuries ^[1]. The defendants are Novo Nordisk, which makes Ozempic, Wegovy and Rybelsus, and Eli Lilly, which makes Mounjaro, Zepbound and Trulicity ^[1]. All of those are brand-name products; the litigation does not cover compounded semaglutide ^[1].

The expert challenges, filed as Daubert motions, were fully briefed after an April 28, 2026 deadline, and summary judgment briefing continued through July 2026 ^[1]. No decision on the expert testimony has been reported. One source describes the admissibility motions as decided on the papers; neither account lists a hearing date or a ruling ^[1][2]. Vision-loss claims involving NAION are handled in a separate MDL, 3163, created in December 2025 and also assigned to Judge Marston. That docket has about 200 cases ^[1][2].

What the evidence shows

Plaintiffs have pointed to a 2023 JAMA study by Sodhi and colleagues, which found that people using GLP-1 drugs for weight loss had 3.67 times the risk of gastroparesis, 4.22 times the risk of bowel obstruction and 9.09 times the risk of pancreatitis ^[1].

In August 2025, after more than 3,700 pages of briefing and evidentiary hearings, Judge Marston issued a 78-page ruling on how gastroparesis must be diagnosed in these cases, requiring objective diagnostic testing ^[1]. According to the National Institute of Diabetes and Digestive and Kidney Diseases, diagnosis requires a gastric emptying study showing more than 10% retention at four hours ^[1].

The FDA added an ileus warning to the Ozempic label in September 2023 ^[1][2]. The two accounts disagree on when the agency added language about severe gastroparesis. One dates the update to October 2025, with the label now stating that Ozempic "is not recommended in patients with severe gastroparesis" ^[1]. The other places the change in January 2025 and notes the label does not state that the drug itself may cause the condition ^[2].

Why it matters for patients

The outcome of the expert challenge does not change whether these drugs are approved or available. It affects whether one theory of harm can be argued in court. If the experts are not allowed to testify, the gastroparesis claims that make up most of the docket lose their central scientific support. If they are allowed, the cases can move toward test trials ^[1].

For patients, the practical detail is documentation. Judge Marston's August 2025 ruling requires objective testing for gastroparesis claims, and a gastric emptying study is described as the strongest evidence for those cases ^[1]. Legal analysts estimate total liability across both MDLs could exceed $2 billion, but that is an estimate, not an outcome ^[1]. No settlements have been announced as of September 2026 ^[1][2].

What happens next

Bellwether trial selection is expected around mid-2026, with the first trials possible in late 2026, depending on how the pending motions are resolved ^[1]. Mass settlements are considered unlikely before late 2027 ^[1]. It has not been disclosed when the court will rule on the expert testimony.