How high would my white blood cell count have to be to be leukemia?

Not high at all: Leukemia is a word that means "white blood". Originally leukemia was recognized when the white blood count was very high. However, as we develop a better understanding, we know that leukemia can be associated with a very low, normal, or high white blood cell count. What is important is the process going on in the bone marrow.

Not too high: Leukemia can be seen at any white blood cell count, high or low. It causes other counts to be low, typically. So low platelets and low red blood cells are typical. But the white blood cell count is extremely variable.

The WBC is always: Elevated in the chronic leukemias - chronic myeloid (CML) and chronic lymphoid (cll). It can be low or very very high in the acute leukemias (aml and all). The number doesn't make the diagnsosis, it is the type of cell and the effect on the other blood elements.

Any number: We diagnose leukemia with white blood cell counts that are low, normal and high. Usually the other blood counts are also affected (low hemoglobin, low platelets).