The hemoglobin at birth is 170 g/L for full-term infants (140 – 200 g/L). After birth, hemoglobin value rises due to low intake and insignificant water loss, which can lead to blood concentration. It usually peaks 24 hours after birth, returns to the level at birth at the end of the first week, and then gradually decreases. Postnatal hemoglobin <145g/L is diagnosed as anemia. The diagnosis of neonatal anemia is as follows: 1. High risk factors for anemia: (1) Family history: Family members have a history of anemia, jaundice and large liver and spleen. (2) Maternal history: history of specific drug exposure, history of infection during pregnancy, etc. (3) Obstetric history: vaginal bleeding, placenta praevia, placenta abruptio, birth injury, etc. (4) History of bleeding in a member of the family: history of maternal-infant blood group incompatibility. (5) Premature infants: history of birth injury and jaundice. (2) Manifestations of anemia: in addition to pallor, neonatal hemolytic disease also has jaundice, hepatosplenomegaly, and even nuclear jaundice. Acute, massive bleeding may be accompanied by shortness of breath, increased heart rate, hypotension, and even shock. In addition to jaundice, internal hemorrhage may be accompanied by corresponding symptoms of the bleeding organ, such as neurological manifestations of intracranial hemorrhage and abdominal masses palpable in subperitoneal hemorrhage. Laboratory tests: (1) Blood count: determine the presence, degree and nature of anemia. (2) Reticulocyte count: reticulocyte count often increases in hemorrhagic or hemolytic anemia, and congenital aplastic anemia should be considered in those with decreased reticulocyte count. (3) Peripheral blood smear: spherocytosis has a spherical cell morphology; hypochromic anemia has an enlarged faintly stained area in the center of the red blood cells. (4) Hemorrhagic anemia: in case of acute blood loss, the hematocrit and reticulocyte count are normal, and the hematocrit decreases after 24-hour hemodilution; in case of chronic blood loss, the hematocrit is normal, the hematocrit decreases, and the reticulocyte count increases. (5) Hemolytic anemia: decreased hematocrit, increased reticulocyte count and bilirubin. (6) Erythropoietic anemia: decreased hematocrit, decreased reticulocyte count, and normal bilirubin level.