Your doctor will take your medical history and perform a physical exam, just like any other evaluation for an illness.

1. Spleen Size
Checking the size of your spleen is an important part of the physical exam. A normal-sized spleen is not normally felt, but an enlarged spleen can be detected on the left side of the upper abdomen, beneath the edge of the rib cage.

The spleen normally stores blood cells and destroys old blood cells. In CML, the spleen may become enlarged because of all the extra white blood cells occupying the organ.

2. Lab Tests
Laboratory tests are also needed. Blood is usually taken from a vein in the arm, and bone marrow is sampled through a procedure called a bone marrow aspiration and biopsy. Your samples are sent to a lab and a pathologist examines them under the microscope and performs other tests, looking to find and further describe the leukemia cells, if present.

Too many white blood cells and abnormal levels of certain chemicals in the blood may be indicative of CML.

In the bone marrow samples, when more blood-forming cells are present that is expected, the marrow is said to be hypercellular. Bone marrow is often hypercellular in CML because it is full of leukemia cells.

3. Gene Tests
Gene testing will also be done to look for "the Philadelphia chromosome" and/or the BCR-ABL gene. This type of test is used to confirm the diagnosis of CML. If you do not have the Philadelphia chromosome or the BCR-ABL gene, then you do not have CML.

4. Imaging Tests
Scans, or imaging tests, are not needed to diagnose CML. However, they might be performed as part of your workup, in some instances; for example, to investigate certain symptoms or to see if there is enlargement of the spleen or liver.