Sheri Ackert worried she might have a new tumor. Steve Hammons stopped taking his blood-thinning medication. Kimberly Toy emptied the pasta and sweets from her cupboards and said: "I can't believe this happened."

What they have in common are dubious test results from Theranos Inc. A review of regulatory records and interviews with patients shows the Palo Alto, Calif., company didn't just burn investors who bought into its promise to…