Everyone sheds hair daily as part of the natural growth cycle, and losing up to about 100 hairs a day is considered normal. Hair loss becomes worth investigating when it is more than usual, persistent, or changes the look of your hair, such as a gradually widening parting, thinning at the crown, a receding hairline, or smooth round bald patches.
Common causes include genetic (pattern) hair loss, hormonal changes, recent illness, surgery, childbirth, significant stress or weight loss (telogen effluvium), thyroid problems, iron deficiency and some medications. Patchy loss can be due to an autoimmune condition called alopecia areata or scalp infections.
See a doctor if hair loss is sudden, patchy, comes with scalp redness, scaling, pain or scarring, or is distressing you. Blood tests and an examination can identify treatable causes, and earlier assessment often gives better results. Avoid unproven remedies. This is general information, not a personal diagnosis.