Low normal red blood cell hemoglobin is commonly seen in iron deficiency anemia, where the patient has microcytic hypochromic anemia. In iron deficiency anemia, especially in the early stages of iron deficiency anemia, the number of red blood cells is normal, but the average volume of red blood cells and the average amount of red blood cell hemoglobin are significantly lower, and eventually a decrease in hemoglobin concentration occurs. In iron deficiency anemia, due to insufficient iron intake, impaired iron absorption and loss of red blood cells, the serum iron concentration in the body is insufficient, and the red blood cells are then unable to use iron normally to synthesize hemoglobin, and eventually the average volume of red blood cells decreases, the amount of hemoglobin contained in each red blood cell decreases, the number of red blood cells does not decrease, and the situation of normal red blood cells and reduced hemoglobin concentration occurs. If iron deficiency anemia continues to develop, or if severe iron deficiency anemia is present, the number of red blood cells will be significantly reduced.