Plasma free hemoglobin of more than one hundred is mildly high, and regular rechecking is recommended. The reference value of plasma free hemoglobin is <50mg/L. When intravascular hemolysis occurs, plasma free hemoglobin is significantly elevated. Mild elevation is common in autoimmune hemolytic anemia and bead protein production disorder anemia. 1. Intravascular hemolysis: hemolytic transfusion reaction, blood group incompatibility transfusion, intravascular hemolysis will occur, resulting in elevated plasma free hemoglobin. 2. Autoimmune hemolytic anemia: the patient's immune dysfunction produces autoantibodies, leading to destruction of red blood cells and release of free hemoglobin into blood vessels, resulting in elevated plasma free hemoglobin. 3. Pearson's dysgenerative anemia: the synthesis of one or more pearson's peptide chains is reduced, and the proportion of pearson's chain is out of balance, which causes too many pearson's peptide chains to form unstable products in red blood cells, leading to hemolysis, and causing the plasma free hemoglobin to be elevated. Plasma free hemoglobin more than one hundred may also exist other causes, it is recommended to consult a doctor in time, with the help of a doctor to clarify the cause of the disease, and targeted treatment or therapy.