In this study, the efficacy of MarrowMAX, a new IVD-certified culture medium for bone marrow samples, was evaluated and compared to the in-house modified culture medium RPMI-1640, which is routinely used at the Academic Hospital in Uppsala for chromosomal analysis. The hypothesis was that the new culture medium MarrowMAX would lead to an increased number of metaphases, resulting in a higher mitotic index, better spreading, and improved metaphase morphology. Twenty patient samples were cultured in parallel using both media and subjected to identical methods for sample preparation and staining for chromosomal analysis. The results demonstrated significant differences between MarrowMAX and RPMI-1640 for one-day, two-day, and three-day cultures. However, no significant differences were observed for directly harvested cultures and overnight colcemid cultures. These findings suggest that MarrowMAX is more effective than RPMI-1640, resulting in a higher frequency of metaphases, which is crucial for detailed chromosomal analysis. This was further confirmed by flow cytometry analysis, showing a higher number of proliferated cells in the MarrowMAX culture compared to the RPMI-1640 culture, in one representative sample. MarrowMAX's enhanced capacity to promote cell growth and structure in a laboratory setting indicates its potential as a promising alternative to RPMI-1640 for future diagnostic applications, potentially leading to faster diagnoses and improved treatment efficacy for patients with hematological conditions.