Hair loss can occur with excessive weight gain or loss in a short period of time or when recovering from a high fever. Hair loss may occur when taking anti-cancer medications. Anemia, due to lack of iron, can cause some hair loss. Hair loss isn't always due to an illness or a medical condition.
Many men have male pattern baldness.
Women can get pattern baldness, too, but it is not as common. This runs in families and usually comes from the mother's side of the family. If you want to know if you are likely to go bald in the future, look at your mother's father to get your best guess. Hair has a limited life span. Each hair usually lives about four to five years and then falls out.