What's more interesting is that the man started writing (finished and published) several full-length novels while he was still in med school to "make a quick buck."
He also was suppose to declare English during his undergrad, but decided against it after he submitted an not-well-known essay written by George Orwell for a class assignment, and the professor gave it a B-. According to him, it was not an act of plagiarism, but a test to verify Harvard English Department's arbitrariness in critiquing literature. Afterwards, I think he dropped English in favor of anthropology (inspiration for Congo), which led him to med school (inspiration for E.R) and then later to a postdoc fellowship in infectious disease (inspiration for Andromeda Strain).
Oh, did I also mention the Crichton was also a star basketball player in high school? The man is quite the renaissance man.
It probably took a lot of work to get there and it must have been an interesting decision for him to leave that profession and start writing.