The hair cycle normally consists of growing, resting and falling hairs and there is a delicate balance between these stages of hair cycle. Normally hair should regrow but if it is not happening, you should consider seeing a dermatologist.
Further information is in the following weblink
https://www.aad.org/public/diseases/hair-and-scalp-problems/hair-loss
Next Steps
Based on the cause of hair loss, certain specific medications can also be started. It also depends on the age of the patient and if planning f or pregnancy or not. Various issues need to be decided before initiating the treatment. The dosage and duration is decided by your dermatologist.