Eli Lilly (LLY) missed Wall Street's revenue expectations in its third quarter earnings released Wednesday morning, which sent shares down more than 13% in early trading — its worst day since Aug. 9, 2000, when the stock sank nearly 30%.

The drugmaker also slashed its profit guidance and the high end of its revenue outlook for the year.

The company reported revenue of $11.4 billion, falling short of Wall Street estimates of $12.17 billion. Still, that represented a 20% increase year over year. The company also missed earnings per share by a whopping 20%, reporting $1.18 per share versus Wall Street expectations of $1.51.

Lilly's blockbuster weight-loss drug Zepbound and diabetes drug Mounjaro remain bright spots, as the GLP-1 drug portfolio remains a focal point of the company's earnings story. But revenue from Zepbound missed analyst estimates of $1.7 billion, with Lilly reporting nearly $1.3 billion.

Eli Lilly said US sales of the two drugs were "negatively impacted by inventory decreases in the wholesaler channel."

CEO Dave Ricks told Yahoo Finance in an interview Wednesday that the company has seen 25% growth in GLP-1s quarter over quarter.

"We need to make enough [supply], and we need better insurance coverage," Ricks said. "Those are the two problems that are slower to change than we want, but those are the gating factors right now."

The FDA took the drugs off the shortage list this quarter, though the agency is reportedly reconsidering the move.

Ricks said the FDA would have no basis to do so since the company is ramping up and planning to finally begin advertising the drug in the US to help promote sales.

"Underlying production is on track to beat our goal of 50% year over year," he said. "We feel really confident in that picture exiting the year [and] into next year. So that's why we're going to be promoting in the US and launching in a few markets ex-US as well."

Mizuho's healthcare expert Jared Holz wrote in a note to clients Tuesday that he expected sales for Zepbound to beat estimates while diabetes drug Mounjaro could slightly miss estimates of $3.8 billion as more patients turn to Zepbound for its higher-dosage weight-loss benefit.

There are concerns that the market overall could be seeing some softness since competitor Novo Nordisk (NVO) also missed expectations last quarter and continues to face some shortages.

"Some have asserted that the stock and group have peaked," Holz wrote. "Given the complexities around much of the Healthcare sector and difficulty establishing a simple thesis for the vast majority of names in Pharma/Biotech or otherwise, we think investors will remain very engaged in weight-loss names."