The Urine Beta-2 Microglobulin (B2M) test measures a small protein in your urine to check kidney tubule health and monitor certain cancers (like blood/bone marrow cancers) or infections, as elevated levels suggest poor kidney filtration (tubular damage) or increased cell turnover from diseases like multiple myeloma or lymphoma. It helps doctors differentiate kidney issues (glomerular vs. tubular), assess tumor burden, and track treatment effectiveness, working alongside other tests