I lost most of my hair how can i stop it?

Hair loss: Hair loss can be caused by stress, chronic illness, genetic causes, pregnancy, too much vitamin A, protein malnutrition, increased male sex hormones, switching or going off birth control pills, anemia, hypothyroidism, vitamin B deficiency, autoimmune diseases, severe weight loss, cancer treatment, medications, vigorous hair treatments, aging. Get blood work and exam. Propecia (finasteride) and minoxidil helps