It was hard to choose an excerpt from this; the whole thing is very much worth reading.

Protections you think you have may not be as broad as you think. The confidentiality that federal health privacy law provides to conversations with a doctor doesn’t always apply to prescriptions. In 2020, Consumer Reports exposed that GoodRX, a popular drug discount and coupons service, was selling information on what medications people were searching or buying to Facebook, Google and other data marketing firms. GoodRX said it would stop, but there is no law against them, or any pharmacy, doing this.

That data becomes even more powerful whenmerged. A woman who regularly eats sushi and suddenly stops, or stops taking Pepto-Bismol, or starts taking vitamin B6 may be easily identified as someone following guidelines for pregnancy. If that woman doesn’t give birth she might find herself being questioned by the police, who may think she had an abortion. (Already, in some places, women who seek medical help after miscarriages have reported questioning to this effect.)

I haven’t even gotten to all the data collected on billions of people by giant technology platforms like Facebook and Google. “Well, don’t use them,” you might say. Again, good luck.

https://www.nytimes.com/2022/05/19/opinion/privacy-technology-data.html