U.S. health inspectors have found serious deficiencies at Theranos Inc.’s laboratory in Northern California, according to people familiar with the matter.

The problems were found during an inspection by the Centers for Medicare and Medicaid Services, the chief federal regulator of clinical labs, at the blood-testing company’s facility in Newark, Calif. Failing to fix the problems could put the Theranos lab at risk of suspension from the Medicare program.

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