It can be detected in a CBC test. But can sometimes be missed
A CBC blood test would show a elevated White Count, which would require a bone marrow biopsy to evaluate the cause. I have Chronic Myelogenous Leukemia, and I felt fine.
I just went for a yearly routine blood test, and the doctor did not like my counts. He immediately did a BMB on me to see what was going on, and thats how they found my CML. That was back in 1998, and I am doing fine. You did not give much information.
Why do you think you might have Leukemia?