Usually two months..You are suffering from hormonal changes causing Androgenetic alopecia causing hair fall. It's completely stoppable even regrowth of hair is possible with certain medications without any side effects. Treatment depends on the grade of hair loss. So, it's a must for diagnosing which grade, you are in for an effective treatment. Please  send photos of your head, by direct online consultation for accurate diagnosis and proper treatment.

To answer your question you have to understand the hair cycle... There are 3 stages in hair cycle.... Active phase... Transition phase and resting phase... The whole process takes 3 months.... In cases of hair loss most of the hair are in resting phase... Minoxidil causes stimulation of hair growth... So the old hair in resting stage falls down giving way for new growing hair to come out.. Hence increased hair shedding is seen in the beginning of minoxidil treatment... By the way for females recommended percentage is 2.and not 5....higher percentage may cause facial hair growth...