Health-Care Companies Are Sending Your Data to Big Tech

California-based health system Kaiser Permanente recently alerted millions of people that their private information was inappropriately shared with tech giants, angering patients who weren’t aware of the practice.

A Bloomberg News analysis showed the same kinds of online trackers remain on the websites of the nation’s largest health-care companies, often unknown to their millions of patients.

Trackers from Meta Platforms Inc.’s Facebook could access patients’ dates of birth and phone numbers on a website for Cigna Group’s pharmacy unit, the analysis found. People signing up for accounts at UnitedHealth Group Inc.’s pharmacy benefit division might have part ...