The way to check the cause of hair loss, specifically as follows: 1, detailed questioning of the patient’s medical history, hair loss time, sleep, shampoo, diet; 2, ask the family history, you can ask your parents or maternal uncle if they have such a history, family history has a certain reference value for androgenetic alopecia; 3, check the degree of hair loss of the patient, whether it is mild, moderate, or severe; 4, baldness, hair pulling test in 10 hair, there is 1 hair does not fall out; if 1 hair pulling test is positive, it means that the patient is in the progressive stage; 5. Hair microscopy to see how many hairs are in 1 hair follicle at the root and the degree of thinning; 6. If the patient has scales, a fungal examination can also be done to rule out ringworm; with the improvement of living standards nowadays, the causes of ringworm disease are becoming less and less; 7. Blood sampling for routine blood, biochemical, thyroid function, and Trace element examination.