Once you start taking hair loss medication, can you never stop for the rest of your life?

I’ve heard rumors that once you start taking hair loss medication, you can’t stop for the rest of your life, and that your hair will fall out the moment you stop. I’m wondering if it’s really true that stopping the medication midway makes the condition worse than before.
I would like to go to the hospital to ask, but I don't have time, so I am asking here.