Serum ferritin is one of the most iron-rich brown protein complexes in the body, with a molecular weight of about 450,000, which contains 17%-23% iron and is one of the main storage forms of iron. It is present in the reticuloendothelial system such as liver, spleen and bone marrow, supplying iron for the synthesis of hemoglobin by bone marrow and releasing it into the serum according to the body’s needs. When a disease occurs in one of the body’s systems, abnormal changes in serum serum ferritin can occur. 1.Relationship with iron deficiency anemia Serum ferritin is the best and most reliable diagnostic method to diagnose occult iron deficiency anemia. 2.Relationship with tumor It is generally believed that serum ferritin in tumor patients is highest in liver cancer, followed by lung cancer, leukemia and malignant lymphoma patients. 3.Relationship with liver and kidney diseases Generally, serum ferritin is significantly higher in the acute phase of acute hepatitis, the active phase of chronic hepatitis and the active phase of cirrhosis, and the more serious the damage to liver cells, the higher the content. In uremic patients, serum ferritin is greater than 250ng/ml in more than 2/3 cases. Most of the anemia caused by uremia is not caused by iron deficiency, but by the greatly reduced erythropoietin when the kidney is damaged, which affects the hematopoietic function as well as iron utilization disorder. 4.Relationship with tuberculosis The measurement of serum ferritin in patients with tuberculosis can diagnose the severity of tuberculosis, guide treatment and estimate prognosis to aid diagnosis. 5.Relationship with heart disease When the concentration of serum ferritin in blood is overloaded, the incidence of heart disease will increase more than 3 times, mainly because the excess serum ferritin promotes the formation of free radicals, which can damage the arterial wall cells and thus damage the heart muscle. Therefore, adults should avoid blind iron supplementation.