Low white blood cells can be detected mainly through routine blood tests. There are many common reasons for low white blood cells, such as severe bacterial infections, severe viral colds, acute and chronic leukemia, acute and chronic lymphoma, and other diseases that may lead to low white blood cells. Therefore, it is not possible to judge a certain disease by a low white blood cell count. It is recommended to further go to the hospital to do lung ct, inflammation index, bone marrow aspiration, CD4CD8 cell count, immunophenotyping and other tests, which will help to further clarify the cause of low white blood cell count.