After her pregnancy, Ms. Guo experienced dizziness and palpitations, and sometimes numbness in her hands and feet. She went to the hospital for examination and laboratory tests revealed anemia. Several parameters of her routine blood test regarding red blood cells were as follows: RBC: 1.83×1012/L; HGB: 79g/L; HCT: 0.23; MCV: 128fl; MCH: 43pg; MCHC: 338g/L. Blood film observation showed a significant increase in the diameter of red blood cells and an increase in the size of multifractional nucleated neutrophils. Ms. Guo was puzzled as to which kind of anemia it was. Based on the above laboratory tests, we initially determined that Ms. Guo might have megaloblastic anemia. Megaloblastic anemia is also a type of anemia characterized by large red blood cell volume, which is the opposite of iron deficiency anemia with small cell hypochromia. We know that in normal people, the volume of red blood cells is usually 80-100 fl and the diameter of red blood cells is 7-8 μm, while in patients with this type of anemia, the volume of red blood cells is often greater than 110 fl, the diameter of red blood cells is often greater than 10 μm or even greater than 15 μm, and the amount of hemoglobin contained in red blood cells increases and the central light-stained area disappears. Megaloblastic anemia is a type of macrocytic anemia caused by folic acid and/or vitamin B12 deficiency. Nutritional megaloblastic anemia accounts for 90% of megaloblastic anemia, with folic acid deficiency accounting for another 90% of the cases, and is more common in pregnant women and infants. There are many causes of megaloblastic anemia, such as: ① Inadequate intake: maternal deficiency of folic acid and/or B12 can cause congenital or acquired inadequate intake in infants and young children, and malnutritional megaloblastic anemia in children mostly occurs within two years of age, 80% of which are due to improper feeding and failure to increase complementary foods on time. ②Increased demand: Infants and children during the growth period, pregnant women, patients with hyperthyroidism, pernicious tumors, leukemia, hemolytic diseases, infections, etc. can increase the need for folic acid and/or vitamin B12, while the actual supplementation is insufficient. ③ Malabsorption: Gastric body or ileal resection, chronic atrophic or erosive gastritis involving the gastric body, or destruction of wall cells due to gastric body cancer infiltration can all reduce vitamin B12 absorption. (4) Impaired absorption and utilization: chronic diarrhea, small bowel resection, restricted ileitis, intestinal tuberculosis, etc. can affect the absorption of vitamin B12 and folic acid; liver disease, acute infection, reduced gastric acid or vitamin C deficiency can affect the metabolism or utilization of vitamin B12 and folic acid. The laboratory tests for megaloblastic anemia are not complicated. First, routine blood tests should be performed, as in the typical case of Ms. Guo’s blood results: the number of hemoglobin and red blood cells is decreased, and the decrease in red blood cells is more obvious than the decrease in hemoglobin, the mean red blood cell volume (MCV) is significantly increased, and the mean red blood cell hemoglobin volume (MCH) is increased, while the mean red blood cell hemoglobin concentration (MCHC) can be be normal. Neutrophils and platelets were normal low or reduced; blood films showed increased erythrocyte diameter and a rightward nuclear shift of neutrophils; bone marrow examination showed active hyperplasia, marked hyperplasia of the red lineage, a giant juvenile variant of red lineage cells, larger than normal cell diameter at all stages of the red lineage, and more mature cytoplasm than nucleus, etc. Similar changes were seen in the granulocyte nuclear megakaryocyte lineage, more pronounced with late juvenile rod-shaped nuclear granulocytes The changes are also seen in granulocytic megakaryocyte lineages, with late juvenile rod-shaped granulocytes being the most obvious. Reticulocytes are normal or mildly elevated. In addition, serum folate and vitamin B12 tests are also very important indicators to confirm the diagnosis. The reference range for folate in normal subjects is 8.6-23.8 mmol/L for men and 7.9-20.4 mmol/L for women, ranging from 2.5-20 ng/ml, and for vitamin B12, 148-660 pmol/L. When these two indicators are significantly lower, there is a high probability that the patient has megaloblastic anemia. In addition, erythrocyte folate measurement, serum homocysteine and methylmalonic acid levels are also useful for the diagnosis of the disease. Once the diagnosis of megaloblastic anemia is made, the cause needs to be identified and then treated according to the specific case. Because the disease is characterized by a deficiency of vitamin B12 or folic acid, treatment with vitamin B12 and folic acid is more effective. The results of routine blood tests, reticulocyte count, folic acid, vitamin B12 and serum potassium need to be reviewed during the treatment process to observe the effect of treatment. Prevention of this disease should start with improving people’s dietary structure and changing their lifestyle habits. Eat more vegetables and foods rich in folic acid and vitamin B12. Folic acid is more abundant in fresh green leafy vegetables, animal liver and kidney, and vitamin B12 is mainly found in animal foods, such as liver, kidney and meat more. Awareness of drug prevention should be raised in susceptible individuals. WHO recommends daily folic acid requirements of 40-50 μg for infants within 6 months, 120 μg for 7-12 months of age, 200 μg for 1-12 years, 400 μg for 13 years and older, 800 μg for pregnant women, and 600 μg for lactation. Such diseases are common in rural areas of northern, northeastern and northwestern China, and in patients with various gastrointestinal diseases and gastrointestinal surgery They also occur frequently in patients with various gastrointestinal diseases and patients after gastrointestinal surgery. Therefore, it is important to eat a reasonable and correct diet and not to be partial, especially for women during pregnancy and infants and children, so as not to let megaloblastic anemia affect your health.