Miss Li was often dizzy and sometimes had difficulty concentrating, but she did not care. During a routine checkup, the doctor said she was anemic, and she was so unsure that she showed me the lab sheet, which showed the following data about the red blood cell test: HGB 68 g/L; RBC 3.60×1012/L; HCT 0.23 L/L; MCV 67 fl; MCH 20 pg; MCHC 280 g/L; RDW 0.176. This obviously abnormal lab sheet told us that Ms. Li was suffering from at least anemia. Her chronic dizziness and palpitations may be related to anemia. The disease that causes anemia can be very insidious, but it can be very serious. If not enough attention is paid to cause further development of the disease, the consequences can be quite serious. From Ms. Li’s laboratory test, her anemia was microcytic hypochromic anemia. After further examination, she suffered from iron deficiency anemia. It turned out that Miss Li had black stool for more than 1 year, and gastroscopy revealed that she had a duodenal ulcer. The cause of the disease is clear, after treatment, Ms. Li quickly healed. Iron is an important trace element in the composition of the human body, but also constitutes an important element of the human red blood cells and hemoglobin. Iron deficiency anemia is a hypochromic anemia caused by the lack of stored iron in the body, or iron utilization disorders. There are many causes of iron deficiency anemia, such as improper feeding of infants and children, paranoid eating and nosebleeds in children and adolescents, excessive menstruation in menstruating women, multiple pregnancies and breastfeeding, and certain pathological factors such as major gastrectomy, chronic blood loss, chronic diarrhea, atrophic gastritis and hookworm infection, etc. Iron deficiency anemia may occur. Certain diseases accompanied by anemia will lead to more serious consequences, decreased quality of life, aggravation of the disease, resulting in poor prognosis and even death. In the routine laboratory work, new cases of anemia can be found practically every day, and many of them may belong to iron deficiency anemia, with children and women being the most frequent patients. Laboratory tests for iron deficiency anemia are convenient and easy to perform, and the initial screening can be achieved by routine blood tests. One of the characteristics of iron deficiency anemia is small-cell hypochromic anemia with variable red blood cell size. Therefore, the first indicators to focus on when performing routine blood tests are the red blood cell count (RBC), hemoglobin (HGB), mean red blood cell volume (MCV), mean cell hemoglobin volume (MCH), and mean cell hemoglobin concentration (MCHC). Generally patients with this disease will have a decrease in red blood cells and hemoglobin, but the decrease in hemoglobin is more significant; another characteristic is the small cellularity and unequal size of red blood cell volume, so MCV will show a significant decrease (often below 80fl, and in severe cases, below 60fl), while RDW will have a significant increase (>15%); in addition, MCH is often below 26pg, and MCHC is often less than 300g/L. The routine blood results of Ms. Li mentioned at the beginning of this article had the above-mentioned characteristics, so it was highly suspected that she had iron deficiency anemia. If the patient’s blood film is further observed, it can be seen that the red blood cell volume is variable in size and the central faintly stained area of red blood cells is enlarged, while the results of white blood cells and classification as well as platelets are normal. Ms. Li also needs to do more laboratory tests related to iron deficiency anemia. There are many other clinical laboratory indicators used to confirm iron deficiency anemia, but experts suggest the following screening indicators are very important for the diagnosis of iron deficiency anemia: ① Serum iron (SI) < 8.95 μmol/L (50 μg/dl); ② Total iron binding capacity (TIBC) > 64.44 μmol/L (360 μg/dl); ③ Transferrin saturation (TS) < 15%; ④ Serum ferritin (SF) <12μg/L. In addition, erythrocyte ferritin measurement <6.5ag/RBC, erythrocyte free protoporphyrin (FEP) >0.9μmol/L or >4.5g/gHb also indicates iron deficiency. If necessary, a bone marrow aspiration is required to confirm the diagnosis. Bone marrow smear shows active hyperplasia, with markedly active proliferation of young red blood cells. The percentage of early and middle-aged red blood cells is increased, the chromatin granules are dense, the cytoplasm is low, and the hemoglobin formation is poor; iron granulocytes are often <10% or absent; and extracellular iron is absent. In order to clarify the cause of anemia or find the primary disease, several fecal occult blood tests, routine urine tests, blood liver and kidney function tests, biochemical or immunological tests, gastrointestinal X-ray, gastroscopy, etc. are also required to determine the cause of iron deficiency anemia. Iron deficiency anemia is not terrible, as long as timely diagnosis, active treatment and eradication of the cause of iron deficiency anemia, you will usually recover easily after iron treatment, and the cost of treatment and diagnosis is not very high. When you feel tired and strained, especially female friends and and children, don't neglect your own and your family's health, go to the hospital early for a routine blood test, and if there are abnormal changes similar to those described above, a more professional confirmatory test for iron deficiency anemia is required. Early detection, early treatment, don't let your health slip away from your side.