The decrease in white blood cells is mainly seen in bacterial infections, viral infections, autoimmune diseases, hematological diseases, etc. How long it takes to rise up depends on the cause of the decrease in white blood cells, combined with clinical manifestations and treatment to be considered comprehensively, which may take about 1 week or 6 months. 1. It takes about 7-10 days for the leukocyte level to return to normal. 2. Viral infections: If the leukocyte decrease is caused by cytomegalovirus and other infections, antiviral drugs such as ganciclovir can be given to treat the decrease, and it takes about 14 days for the leukocyte level to return to normal. 3. Autoimmune diseases: For example, rheumatic immune diseases, including systemic The leukocyte level can be restored to normal in about 1 month after glucocorticoid treatment such as prednisone acetate is given; 4. Blood system diseases: If the leukocyte reduction is caused by aplastic anemia, the leukocytes will rise slowly after symptomatic treatment with leukocyte-raising drugs, and the leukocyte level can return to normal after about half a year when the bone marrow function is restored. The white blood cell level can return to normal. The normal value of leukocytes is (4.0-10.0)×10^9/L. If the leukocytes are lower than 3.0×10^9/L, the diagnosis of leukocytopenia can be made. It is recommended to eat nutrient-rich substances such as eggs, lean meat, dairy products, etc., fresh vegetables and fruits, do not drink alcohol and do not eat spicy and stimulating food.