Anemia is mainly characterized by a decrease in the number of red blood cells and a decrease in hemoglobin. The severity of anemia is clinically judged by the degree of hemoglobin reduction. The symptoms of anemia are related to the degree of anemia and the speed of occurrence of anemia. Mild cases may have no obvious symptoms and are detected during routine physical examination. The main manifestations of anemia are: (1) Skin and mucous membrane changes: pale lips, mucous membranes, nail beds, and yellow staining when hemolysis is present. (2) Nervous system: dizziness, tinnitus, headache, insomnia, dreaminess, memory loss, inattention, etc. In children, anemia may cause crying and restlessness and even affect intellectual development. (3) Respiratory and circulatory system: Mild anemia has no obvious manifestations, but only accelerated breathing and deepening of the heart rate after activity. The heavier the anemia, the greater the activity, the more obvious the symptoms. In severe anemia, even in a calm state, there may be shortness of breath or even seated breathing and other manifestations of heart failure. (4) Digestive system: Anemia can lead to reduced digestive function, indigestion, abdominal distention and reduced appetite. Iron-deficiency anemia may lead to foreign body sensation or heterophilia in swallowing. Megaloblastic anemia or pernicious anemia can cause tongue inflammation, tongue atrophy, beef tongue, mirror tongue, etc. (5) Urinary system: Acute hemolysis can lead to hemoglobinuria and ferric hemoglobinuria (soy sauce-colored urine), and in severe cases, free hemoglobin can even block the renal tubules, which can lead to oliguria, anuria, and even acute renal failure.