Enlarged lymph nodes cannot be detected by routine blood tests. Generally speaking, enlarged lymph nodes can be detected by palpation, imaging, lymph node puncture, etc. Blood test results can only help to determine the cause of enlarged lymph nodes. Lymph nodes can be categorized into superficial lymph nodes and deep lymph nodes. Superficial lymph nodes that are enlarged can be observed with the naked eye and then palpated with the hands to get a preliminary understanding of the lymph nodes, such as their morphology, size, pressure and pain, and mobility, etc. Deeper lymph nodes can be examined by ultrasonography, CT, MRI, etc. If malignant changes are suspected, then a diagnostic examination can be performed. If malignancy is suspected, lymph node biopsy should be performed to determine whether the lymph node metastasis is caused by the tumor. Routine blood tests can help determine the cause of enlarged lymph nodes. If the routine blood test suggests an increase in white blood cells, especially neutrophils, the enlarged lymph nodes may be caused by bacterial infection. If the increase in leukocytes in the routine blood test is dominated by lymphocyte proliferation, then it may be a viral infection, such as cytomegalovirus infection, EBV infection and so on. It is recommended that once the presence of enlarged lymph nodes is detected, it is necessary to go to the hospital in time to avoid delaying the condition.