She insisted Theranos had made changes aimed at addressing regulators’ concerns over the accuracy of its tests. “We’ve taken comprehensive corrective measures over the past several months,” she said. If Medicare chooses to impose sanctions on the company, she said, Theranos will continue to work with regulators to address its concerns.

Theranos, the creation of Ms. Holmes, epitomized the promise of Silicon Valley to transform — or disrupt, to use its own lingo — all of health care. Having dropped out of Stanford University to found the company in 2003, Ms. Holmes claimed to have created a whole new way to perform multiple tests using a few drops of blood from a finger prick, which would be less painful and less costly than conventional blood tests.

Her vision of bringing laboratory testing to the masses, including allowing customers to order tests without a doctor’s order, attracted some well-known venture capitalists. The company earned a stunning $9 billion valuation and an abundance of news media attention. Ms. Holmes graced the cover of numerous magazines, including T: The New York Times Style Magazine.

A scathing report in The Wall Street Journal last October put an end to the fairy tale and Theranos scrambled to respond to the news media’s sudden turn. The company’s fall from grace came to symbolize the overreach of Silicon Valley and the hype that surrounds unproven technology.

While Ms. Holmes has continued to defend the company in as many forums as she can, the lack of hard information about whether the technology worked has only increased the skepticism surrounding her company.

Examiners from Medicare inspected Theranos’s laboratory in Newark, Calif., last fall and found numerous deficiencies, one of which they said posed “immediate jeopardy to patient health and safety.”

That particular deficiency related to Theranos’s test for the clotting ability of blood, a measurement used to help determine the correct dose of the blood-thinning drug warfarin. Too much warfarin can cause internal bleeding while too little can leave a patient vulnerable to a stroke. The inspection report, which was recently made public by Medicare, said that all 81 results provided to patients from that test from April to September of last year were inaccurate.