Anemia is a medical condition defined by a reduced concentration of red blood cells or hemoglobin in the blood, resulting in a lower-than-normal oxygen-carrying capacity. This deficiency can stem from multiple sources, including insufficient intake of essential nutrients such as iron or certain B vitamins, chronic blood loss, or systemic issues that impair the body's ability to manufacture adequate blood components. The resulting decreased oxygen delivery to tissues and organs often manifests through symptoms such as persistent fatigue, weakness, paleness, and shortness of breath. Diagnosis involves analyzing blood samples to quantify the hemoglobin level and identify the underlying cause to guide appropriate treatment.