When you see a question here that you know for a fact is answered incorrectly, do you correct the poster?

For example, someone asks about something on their face, posts a pic and a jelly says Oh no, you have a tumor! Now, you know, in fact that is just a big honking zit. Do you correct the person who misidentifies or gives wrong advice? A jelly may give advice on medications to take and you know this medication isn’t to be taken by all. Do you hop in and say, “but you should make sure you see a doctor to make sure this doesn’t conflict with any other medications you are taking”?
I’m not talking about bad relationship advice or misidentifying a movie or a song, but something that could potentially hurt someone.
I’ve noticed this on a few occasions, but never say anything. How, or do you, handle this?