Elizabeth Holmes says that her test can help detect ailments from just a few drops of blood. Photograph by Jenny Hueston

One afternoon in early September, Elizabeth Holmes took the stage at TEDMED, at the Palace of Fine Arts, in San Francisco, to talk about blood. TEDMED, a part of the Technology, Entertainment, and Design enterprise, is an annual conference devoted to health care; its speakers span a range of inquiry from Craig Venter, the genomic scientist, discussing synthetic life, to Ozzy Osbourne discussing his decision to get his entire genome sequenced. The phrases “disruptive technology” and “the future of medicine” come up a lot.

Holmes, who is thirty, is the C.E.O. of Theranos, a Silicon Valley company that is working to upend the lucrative business of blood testing. Blood analysis is integral to medicine. When your physician wants to check some aspect of your health, such as your cholesterol or glucose levels, or look for indications of kidney or liver problems, a blood test is often required. This typically involves a long needle and several blood-filled vials, which are sent to a lab for analysis. Altogether, diagnostic lab testing, including testing done by the two dominant lab companies, Quest and Laboratory Corporation of America, generates seventy-five billion dollars a year in revenue.

Holmes told the audience that blood testing can be done more quickly, conveniently, and inexpensively, and that lives can be saved as a consequence. She was wearing her daily uniform—a black suit and a black cotton turtleneck, reminiscent of Steve Jobs—and had pinned her hair into an unruly bun. As she spoke, she paced slowly, her eyes rarely blinking, her hands clasped at her waist. Holmes started Theranos in 2003, when she was nineteen; she dropped out of Stanford the following year. Since then, she told the audience, the company has developed blood tests that can help detect dozens of medical conditions, from high cholesterol to cancer, based on a drop or two of blood drawn with a pinprick from your finger. Theranos is working to make its testing available to several hospital systems and is in advanced discussions with the Cleveland Clinic. It has also opened centers in forty-one Walgreens pharmacies, with plans to open thousands more. If you show the pharmacist your I.D., your insurance card, and a doctor’s note, you can have your blood drawn right there. (The sample is then sent to a Theranos lab.) From that one sample, Holmes said, several tests can be run—all less expensive than standard blood tests, sometimes as much as ninety per cent below the rates that Medicare sets. A typical lab test for cholesterol can cost fifty dollars or more; the Theranos test at Walgreens costs two dollars and ninety-nine cents.

In conversation, Holmes speaks in a near-whisper; onstage, her voice drops an octave and takes on a formal instructional cadence. The TEDMED crowd listened intently as she spelled out what she sees as the shortcomings of the existing blood-testing business. The tests are too costly, are available at inconvenient times or places, and involve unpleasant syringes. Holmes has an aversion to needles, and her mother and her grandmother fainted at the sight of them and at the sight of blood. Recently, she told me, “I really believe that if we were from a foreign planet and we were sitting here and said, ‘O.K., let’s brainstorm on torture experiments,’ the concept of sticking a needle into someone and sucking blood out slowly, while the person watches, probably qualifies.”

Holmes thinks that getting a blood test should instead be a “wonderful” experience, and the aim of Theranos is to lower the barriers. She told the crowd that between forty and sixty per cent of people who are ordered by their doctor to get a blood test do not. Diabetes, sexually transmitted diseases, and other common medical conditions could be diagnosed and treated earlier if the tests were less onerous and more accessible, she said. “We see a world in which no one ever has to say, ‘If only I’d known sooner.’ A world in which no one ever has to say goodbye too soon.”

Theranos, which is privately held, is both a hardware company and a medical company, and for many years it has operated with a stealth common to many Silicon Valley startups. “For a long time, I couldn’t even tell my wife what I was working on,” Channing Robertson, a chemical-engineering professor at Stanford and the company’s first board member, told me. In recent months, Holmes has been giving similar versions of her TEDMED presentation in talks and interviews around the country. Investors have valued the company at more than nine billion dollars, comparable to the two major diagnostic labs. Holmes owns more than fifty per cent of the company; she was profiled last spring in Fortune and subsequently featured in Forbes as “the youngest self-made female billionaire in the world.” The board of her company is stocked with prominent former government officials, including George P. Shultz, Henry Kissinger, Sam Nunn, and William H. Foege, the former director of the Centers for Disease Control and Prevention. Dr. Delos M. Cosgrove, the C.E.O. and president of the Cleveland Clinic, is an avid supporter. “I think it’s potentially a breakthrough company,” he told me. “It represents a major change in how we deliver health care.”

The company’s rise comes at a time when consumers are increasingly eager for access to their personal data. The plummeting costs of DNA-sequencing technology have made it possible for companies such as 23andme to provide individuals with their genetic information directly, rather than through doctors, empowering nerdy customers and self-motivated patients. Smartphone apps let users track their heart rates, their sleep cycles, and the number of steps they’ve taken, and share the data with a doctor or with friends. In her talk, Holmes said, “My own life’s work in building Theranos is to redefine the paradigm of diagnosis away from one in which people have to present with a symptom in order to get access to information about their bodies to one in which every person, no matter how much money they have or where they live, has access to actionable health information at the time it matters.” Cosgrove predicts that blood tests for many common health issues, including high cholesterol and diabetes, will be initiated by patients as well as by doctors. “The CVSs and the Walgreens and the Walmarts of the world are going to be taking a lot of things that currently go to primary-care physicians,” he said. “The impact of that on our industry will be enormous.”

But unfiltered medical data aren’t a pure virtue. Last year, the U.S. Food and Drug Administration barred 23andme from disseminating some information out of concern that consumers might misunderstand or misuse it. Some observers are troubled by Theranos’s secrecy; its blood tests may well turn out to be groundbreaking, but the company has published little data in peer-reviewed journals describing how its devices work or attesting to the quality of the results. “It’s trying to apply the Steve Jobs way of keeping everything secret until the iPhone was released,” Lakshman Ramamurthy, a molecular biologist and a former associate director at the F.D.A., told me. “But a health test is more consequential than a consumer product. It needs to be clinically valid and provide useful information.”