Answer: A normal leukocyte level number ranges from 3,500 to 10,500 in a microliter of blood or 3.5-10.5 x 10 9/L. The final number depends on your race, age, and time of day that it was tested. The statement: “except for low leucocytes (589)” is a bit difficult to understand depending on the measurement as we don’t routinely see the number expressed like that—does the level actually show 589 white blood cells in a microliter of blood? How is the differential count of the white blood cells? Are the neutrophils or the lymphocytes low? (neutrophils and lymphocytes are subtypes of white blood cells). In any event, is it expected that chemotherapy can bring your numbers low (your white cells, your red blood cells, and your platelet count can go low requiring transfusions or the use of growth factors like neupogen). It takes several weeks to months to completely allow your bone marrow to recover its fully functioning state. Since the last time you had chemotherapy was 2 years ago, it is possible that your doctor just wants to see the trend of the white blood cells over time. You didn’t mention if you had any new symptoms or an infection, but I am assuming no other symptoms were present at your last visit. We have had patients with HCL that had an episode of low white blood cells that over time resolved on its own—we only monitored their numbers and after a while the numbers went back to a normal level. If the number of white blood cells remains in the low level, your doctor may want to repeat a bone marrow biopsy to see if there is evidence of disease recurrence or another reason for the low white blood cells—sometimes certain medications can affect your total number of white blood cells.