Why could someone require a bone-marrow biopsy?

Many Indications. Bone marrow biopsy is most useful in diagnosis and staging of blood cancers (leukemia, lymphoma, multiple myeloma, etc). Also indicated for evaluating unexplained anemia, leukopenia, thrombocytopenia, pancytopenia, or unexplained elevated blood counts. It is also useful for fever of unknown origin, or as a confirmation that bone marrow transplantation is successful.
Blood disorders. The most common reason for having a bone marrow biopsy is to investigate an issue with your blood cell counts like in anemia or leukemia (excessive increase in one of blood cell types). In patients with advanced types of cancer, bone marrow bx is done to rule out its involvement or to assess the effect of chemotherapy on blood cell production.
Blood making cells. The bone marrow is where the red blood cells, white blood cells, and platelets are made. A bone marrow biopsy is often recommended when a physician, usually a hematologist or oncologist, needs to see what might be causing an abnormality in ones complete blood count (cbc).