How long it takes to recover from a leukocyte count of 2.8×10^9/L depends on the specific cause, the presence of blood disorders, etc. Normally, the number of white blood cells is between (4.0-10.0) x 10^9/L. If it shows 2.8 x 10^9/L, then it is mild hypocellularity. There are many clinical causes of hypocellularity. If it is induced by a cold or medication and is not combined with other blood disorders, it can gradually return to normal in about 3-5 days after the cold symptoms are relieved or the medication is stopped. If the hypocellularity is caused by a malignant disease, such as myeloproliferative disorder, the patient may not be able to fully recover to normal levels until the disease is completely cured because of the disorder in the hematopoietic system itself. In the case of leukopenia caused by radiotherapy, it can gradually return to normal levels in about 2-4 weeks after taking white-raising drugs. After leukopenia occurs, patients need to go to the hematology department of the hospital in a timely manner and carry out reasonable and effective treatment in combination with relevant clinical examinations, and should not use drugs on their own to avoid aggravating or delaying the disease.