Anemia is a medical condition caused by a lack of red blood cells or hemoglobin in the body, which can lead to lethargy and fatigue. It is one of the most common causes of lethargy and can be caused by a variety of factors, including dietary deficiencies, certain medications, and chronic illnesses. ANEMIA can also be caused by blood loss due to trauma or surgery. Treatment for ANEMIA typically involves increasing iron intake, taking vitamin supplements, and making lifestyle changes.