Patients with iron-deficiency anemia can exhibit symptoms of fatigue. Anemia is characterized by red blood cells and hemoglobin levels that are below the normal range. Red blood cells are the main cells responsible for transporting oxygen in the body. Oxygen enters the blood through gas exchange in the lungs and is then delivered throughout the body by red blood cells to supply oxygen. Therefore, patients with anemia will show varying degrees of ischemia and hypoxia. In the nervous system, this can be manifested as lethargy, insomnia, frequent dreaming, tinnitus, blurry vision, fainting, and lack of concentration. As the severity of anemia increases, these symptoms may also worsen. Patients with severe anemia may exhibit significant lethargy and drowsiness.