Losing 100 hairs per day is considered normal. In general, hair loss exceeds 100 hair strands per day. There are many reasons for hair loss.
Diseases (thyroid disease, diabetes, iron deficiency anemia), nutritional disorders, vitamin deficiency, some medications, and stress from environmental and social life can cause hair loss.
Male pattern hair loss (Androgenetic Alopecia) is the most common type of hair loss. Although it is more common in men, it can also be seen in women.
The main cause of hair loss in women is diseases and especially iron deficiency anemia.