Leukocyte 3.5 means that the peripheral blood leukocyte count is 3.5×10^9/L. Compared with the normal range, leukocyte 3.5 is a mild leukopenia, which is considered low. The normal value of peripheral blood leukocyte count is 4.0×10^9/L~10.0×10^9/L. Some normal people’s leukocyte count may be slightly lower than the lower limit of leukocyte normal value, and leukocyte 3.5 is not considered to be low, and it does not necessarily mean that they are suffering from some kind of disease, so they do not need to be treated specially. If the white blood cell 3.5×10^9/L is caused by viral infection, hypothyroidism, rheumatoid arthritis and other immune diseases, timely control of infections, drug treatment, etc. can make the white blood cell return to normal level. If leukocyte 3.5×10^9/L is caused by acute myeloid leukemia, myelodysplastic syndrome and other malignant diseases, active treatment of the primary disease is needed.