When did everyone go to the doctor for early-stage hair loss?

Recently, my hair has been getting thinner and falling out more, so I am worried that I might be in the early stages of hair loss.
It bothers me that the crown of my head looks sparse and my parting seems to be getting wider.
It isn't severe yet, but I'm not sure if I should go to the hospital.
I am curious to know at what stage of symptoms everyone sought medical attention.
I would also like to know if the treatment is more effective if I go early.
I'm curious if there are people who manage with just shampoo or home care.
Please share your experience regarding when you started hair loss treatment.