Blood test can detect infectious diseases, metabolic diseases, hematologic diseases and so on. 1. Infectious diseases: respiratory diseases, such as upper respiratory tract infections, pneumonia (bacterial, viral), bronchitis, etc.; digestive diseases, such as hepatitis. 2. Metabolic diseases: including hyperlipidemia, diabetes mellitus, diabetic ketoacidosis, gout, hypoglycemia, hypercalcemia, and so on. 3. Blood system diseases: including anemia, such as iron deficiency anemia, megaloblastic anemia, aplastic anemia, etc.; thrombocytopenic purpura; thrombocytosis; true erythrocytosis; leukemia, etc. In addition to the above diseases, blood tests can also detect many diseases such as syphilis and AIDS. If a certain disease appears, it is recommended to go to the hospital in time to receive formal examination and early formal treatment.