The agency reviewed 30 post-marketing reports of acute pancreatitis, which is an inflammation of the pancreas that can be fatal. After deciding an association is “suspected in some of these case,” the FDA has asked Amylin Pharmaceuticals, to revise the label.

A spokeswoman for Lilly, which co-markets the diabetes med, tells Reuters the risk of pancreatitis was included in Byetta’s label late last year. “What you’re seeing today is a clarification of language to show that severe and persistent abdominal pain could be a sign of something serious like pancreatitis” and require medical attention, says Kindra Strupp. The pancreatitis cases were “rare”, she maintains, given that Byetta has been taken by 700,000 people worldwide since being approved in 2005.

The FDA says that, of the 30 reports of pancreatitis, 27 patients had at least one other risk factor for developing the condition, such as gallstones or alcohol use, according to The Wall Street Journal. In six cases, symptoms of pancreatitis began or worsened soon after the dose of Byetta was increased from 5 micrograms twice daily to 10 micrograms twice daily, the FDA told the paper. In 22 of the 30 cases, reports indicated patients improved after discontinuing Byetta.

Byetta is a twice-daily injection that was approved for Type 2 diabetics who didn’t respond to other meds. The drug generated sales of $430.2 million last year, accounting for 90 percent of Amylin’s revenue and representing one of the Lilly’s fastest-growing meds, according to Bloomberg News.