Blood routine changes of tumor patients are affected by patients’ tumor pathological type, malignant degree, treatment plan such as chemotherapy, immunotherapy, radiotherapy, etc. There may be a decrease in three series; only hemoglobin may be decreased; there may also be an increase in leukocytes and neutrophils. 1. Radiotherapy for cancer patients often leads to bone marrow suppression, and blood routine shows that white blood cells, hemoglobin and platelets are lowered. In mild cases, attention should be paid to rest and not to be infected; in serious cases, the drugs should be stopped and timely consultation and treatment should be carried out. 2. If cancer patients bleed from necrotic masses, blood routine may show that only hemoglobin is reduced, and then they need to consult the doctor in time for hemostasis treatment. 3. Cancer patients with lowered immunity often have bacterial and viral infections, at this time, blood routine can show elevated leukocytes and neutrophils, in addition, patients are often accompanied by paraneoplastic syndrome, which affects multiple tissues and organs, leading to fever, rash, tumor necrosis, causing inflammation, which can also cause elevated leukocytes and neutrophils. Blood routine laboratory changes in tumor patients, specific should consult a professional oncologist. If there is any discomfort, consult the doctor in time to avoid delaying the treatment.