The Beta-2 Microglobulin Test is performed to diagnose multiple myeloma and renal tubular disorders along with other immune diseases. It is a serum(blood) and urine test to measure the levels of Beta-2 Microglobulin in bloodstream or urine. Beta-2 microglobulin is a cell membrane protein, exists in a protein complex termed MHC-1 (HLA in humans). During an immune response, MHC proteins, as well as Beta-2 microglobulin levels, increase. So this test works as a tumor marker for some hematologic malignancies. This protein is filtered by kidneys. But dysfunctionality hampers the filtration process and it results in elevated B2M level in urine. However, this particular test may not diagnose specific disease but provides doctor with patient’s prognostic information. The Beta-2 microglobulin serum test is combined with a urine test to determine the prognosis of multiple myeloma. In other words, higher levels of B2M may depict advanced stage of myeloma.