Beta-2-microglobulin (ß2M) is a protein found on the surface of all cells. Small amounts are shed into the serum and are usually filtered out by the kidneys. Increased amounts are found in the serum of patients with kidney disease, lymphomas, some leukemias, and myelomas.

Of interest is the prognostic connection that is sometimes seen with this protein, especially with myeloma, but in the other conditions as well. People diagnosed with these diseases and who have levels of beta-2-microglobulin below 2.0 (2mg/L) seem to have at least 2 more relatively complication-free years. Beta-2-microglobulin is evaluated via a normal blood draw.