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What is Beta-2 Microglobulin (B2M) Serum test? 

Beta-2 Microglobulin is a protein that is present on the surface of most cells in the body. It is constantly shed in some amounts into the blood, though the highest amount is shed by beta lymphocytes (a type fo WBCs) and tumour cells. Thus, B2M levels rise drastically when the immune system is activated (leading to an increase in WBCs) or with diseases that tend to increase cell production and destruction.

The level of B2M is also seen to be high in patients with cancers such as multiple myeloma and lymphoma or with inflammatory disorders and human immunodeficiency virus (HIV) infection. 

This test measures the levels of beta-2 microglobulin in your serum - the liquid part of blood after separating RBCs. It helps detect if you have a tumour or cancer.

When the blood gets filtered through kidneys, most of the B2M passes through the glomerular membrane, the filters of kidneys, but gets retained by renal tubes (the part of kidneys that reabsorbs water and nutrients). Normally a small amount of B2M goes into the urine. However, if the glomerular membranes are not functioning properly, all the B2M would be retained in the blood. So this test also helps assess kidney function.

  1. Why is a Beta-2 Microglobulin (B2M) Serum test performed?
  2. How do you prepare for a Beta-2 microglobulin (B2M) test?
  3. How is a Beta-2 microglobulin (B2M) test performed?
  4. Beta-2 microglobulin (B2M) test results and normal range

Doctors order the B2M test as a follow-up test for people who have recently been diagnosed with multiple myeloma. This is done to assess the stage of the disease and evaluate the effectiveness of the treatment that is being given. It is also useful for determining the presence of tumours

Additionally, your doctor may order this test, along with a B2M urine test if you show the following signs of kidney damage:

Since high Beta-2 microglobulin in urine indicates damage in the renal tubes (due to reduced B2M absorption through renal tubes), together, the two tests help find out the exact location of the damage.

(Health checkup app)

You do not require any special preparation for this test. 

Your doctor or a laboratory technician will use a sterile needle and withdraw a few milliliters of blood from a vein in your arm. He/she may tie a tourniquet over your upper arm first to locate the right vein - the tourniquet would make the vein to temporarily swell up so it becomes easier to put a needle in it. Sometimes, more than one needle insertion is required. Once enough blood is collected, the band will be removed from the arm.

You may feel a bit dizzy or lightheaded after the test or notice a bruise at the needle insertion site - they will go away on their own. 

Normal results:

The normal values for B2M in serum are between 1.21 and 2.70 mcg/mL. Low levels of B2M are considered to be normal. 

Abnormal results:

If there is an increase in the level of B2M in the blood then the results are considered to be abnormal. Serum B2M results may be elevated in benign conditions such as renal dysfunction, some viral infections or chronic inflammation. 

If the test was done to assess the cancer stage, the results will be evaluated accordingly. 

  • In patients with multiple myeloma, serum B2M of <4 mcg/mL is indicative of a good prognosis.
  • If the effectiveness of the treatment is being determined, then an increasing B2M level may mean that the cancer is spreading. Similarly, a drop in serum B2M level indicates that the treatment is working.
  • If the serum B2M levels have neither increased nor decreased, then this may mean that the disease is stable.
  • If the B2M levels decrease but later increase after cancer treatment, this may mean that the cancer has returned.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.


  1. American Cancer Society [internet]. Atlanta (GA), USA; Cancer Staging
  2. American Cancer Society [internet]. Atlanta (GA), USA; Multiple Myeloma Stages
  3. Wu AHB. Tietz Clinical Guide to Laboratory Tests. 4th ed. St. Louis: Elsevier Saunders.
  4. Pagana KD, Pagana TJ. Mosby’s Diagnostic and Laboratory Test Reference. 13th ed. Mosby, Inc., Saint Louis, MO.
  5. Bataille R, Magub M, Grenier J, et al. Serum beta-2-microglobulin in multiple myeloma: Relation to presenting features and clinical status. Eur J Cancer Clin Oncol 1982;18:59-66. PMID: 6177535.
  6. Garewal H, Durie BG, Kyle RA, et al. Serum beta-2-microglobulin in the initial staging and subsequent monitoring of monoclonal plasma cell disorders. J Clin Oncol 1984;2:51-57. PMID: 6366146.
  7. Norfolk D, Child JA, Cooper EH, et al. Serum beta-2-microglobulin in myelomatosis: potential value in stratification and monitoring. Br J Cancer 1980;42:510-550. PMID: 6159910.
  8. Dolan MJ et al. Early markers of HIV infection and subclinical disease progression. Vaccine. 1993;11(5):548-51. PMID: 8098175.
  9. Karlsson FA, Wibell L, Evrin PE. Beta-2-microglobulin in clinical medicine. Scand J Clin Lab Invest 1986;154:27-37. PMID: 6163193.
  10. Greipp PR, Katzmann JA, O'Fallon WM, Kyle RA. Value of beta-2-microglobulin level and plasma cell labeling indices as prognostic factors in patients with newly diagnosed myeloma. Blood 1988;72:219-223. PMID: 3291982.

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