Hematopoietic Stem Cells (HSCs) are the responsible to replenish mature blood cells after hematopoietic stresses. One of the most common dose limiting adverse effects in cancer treatment is myelosuppression, which describes adverse effects on the blood forming system. Here, we provide an assay to measure depletion of different subsets of CD34+ progenitors in Normal Bone Marrow (NBM) or other hematological diseases to potentially screen drug candidates and combinations for hematotoxicity, as well as personalize therapy to the individual sensitive patient at risk.