Beta 2 Microglobulin (B2M) Tumor Marker Test
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A beta-2 microglobulin tumor marker test measures the amount of a protein called beta-2 microglobulin (B2M) in your body fluids. The test usually uses a sample of your blood. It may also be done using urine (pee) or in rare cases cerebrospinal fluid (CSF).
B2M is a small protein found on the surface of most cells in your body. Your cells release B2M when they are damaged or when they grow more quickly than normal. Usually, your kidneys filter B2M out of your blood.
So, only small amounts of this protein are present in healthy people. However, B2M is also a type of tumor marker. Tumor markers are substances that are often made by cancer cells or by normal cells in response to cancer.
High levels of B2M in body fluids are often caused by blood and bone marrow cancers, such as: Multiple myeloma.; Chronic lymphocytic leukemia (CLL).; Certain types of lymphoma.; High B2M levels can also be caused by noncancerous conditions, such as kidney disease and autoimmune disorders. Because high levels of B2M can be caused by such a wide variety of conditions, health care providers don't use the results from a beta-2 microglobulin tumor marker test to diagnose cancer or any other condition. Instead, it is often done after you've been diagnosed with certain cancers of the bone marrow or blood.
Why this test is done
You may need this test if you've been diagnosed with multiple myeloma, chronic lymphocytic leukemia, or certain types of lymphoma. A B2M test can help determine how serious your disease is, monitor your cancer over time, and check how well your treatment is working.
If you have multiple myeloma, a urine test for B2M may be used to see if your disease is affecting your kidneys.
How to prepare
For blood and urine tests, there are no special preparations.
For a CSF analysis (spinal tap), you may be asked to empty your bladder (pee) and bowels (poop) before the test.
Sample type
Blood Urine CSF
Other names for this test
total beta-2 microglobulin, β2-microglobulin, B2M, B2MG, thymotaxin
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Educational content only. This entry describes what a test measures and how published reference ranges are defined. It is not a diagnosis, does not interpret your personal results, and is not a substitute for a qualified doctor.