Sure every person must do their hishtadlus.
But in regards to a doctor or medicine, if someone is on a high level like a gadol hador and he wouldn’t take the medicine for him it wouldn’t be a lack of hishtadlus cause the tzaddik doesn’t just know that only Hashem can heal him. The pills are like avoda zara to him so it’s not a lack of hishtadlus.
May you one day reach this high level of a gadol hador and start to realize that every act in your life and every breath you take is a gift and coming directly from Hashem. (not only cause you went shopping or made money. Everything comes from Hashem it’s just a matter of how Hashem sends it to you. One person can make a million dollars from 20 years of work at 50k a year and another person Hashem can send in an instant with a lottery ticket winner that just happened in Israel last week to a poor man and it was his first lottery ticket he bought in his life, he didn’t always buy tickets all year long)