Hair shedding is common, but a sudden increase, widening part, patchy loss or persistent thinning can sometimes reflect more than a cosmetic concern. Hair loss has many possible causes, and the pattern and timing often matter more than any single symptom.
The American Academy of Dermatology lists thyroid disease and low levels of iron, protein, zinc or biotin among potential causes. Illness, surgery, childbirth and severe emotional stress can also trigger temporary shedding several months after the event. Hormonal changes, autoimmune conditions, scalp inflammation, certain medicines and damaging hair practices may contribute as well.
Diagnosis comes before treatment
Hair loss alone cannot confirm thyroid disease, anemia or another condition. A clinician may review medical and family history, diet, recent illness, medicines and hair-care practices before examining the scalp. Depending on the pattern, testing may include blood work, a hair-pull assessment or, less commonly, a scalp biopsy.
Changing shampoo or taking supplements without identifying the cause may delay appropriate care. Excess nutrients can also be harmful, so supplements should not be treated as a universal solution.
When to seek medical advice
Consider speaking with a primary-care clinician or dermatologist when hair loss is sudden, patchy, painful, accompanied by scalp redness or scaling, or continues without an obvious explanation. Early assessment is particularly important when there are other symptoms such as fatigue, weight changes, menstrual irregularity or signs of inflammation.
Many causes are treatable or reversible, but the correct approach depends on an accurate diagnosis.