Also Known As
B2M
B2M
β2-Microglobulin
Thymotaxin
Formal Name
Beta2 Microglobulin, Serum, Urine, or CSF
This article was last reviewed on
This article waslast modified on 5 August 2021.
At a Glance
Why Get Tested?

To help evaluate the severity and prognosis of certain cancers, including multiple myeloma and lymphoma

When To Get Tested?

When you have been diagnosed with multiple myeloma or certain other cancers; sometimes to monitor disease activity and treatment

Sample Required?

/node/297A blood sample is obtained by inserting a needle into a vein in the arm. A 24-hour urine sample may also be collected. Rarely, a CSF sample may be collected from the lower back using a procedure called a lumbar puncture or spinal tap

Test Preparation Needed?

No test preparation is needed

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Beta-2 microglobulin (B2M) is a protein that is found on the surface (part of MHC class I) of almost all cells in the body and is shed by cells into the blood, particularly by B lymphocytes and tumour cells. It is present in most body fluids and its concentration in the bloodstream rises with conditions that increase cell production and/or destruction, or that activate the immune system. This test measures B2M in the blood, urine, or rarely in the cerebrospinal fluid (CSF).

B2M is frequently elevated in the blood with cancers such as multiple myeloma and lymphoma, with inflammatory disorders and infections (e.g., HIV, CMV) and in kidney disease. It is useful as a tumour marker because it provides prognostic information in blood cell cancers. Though it can be used to assess kidney function, this article focuses on its use as a tumour marker.

The B2M concentration can be increased in the CSF of individuals with blood cell cancers that have spread (metastasised) to the brain, such as lymphoma, but also with some chronic disorders such as multiple sclerosis and with viral infections such as HIV.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. A 24-hour urine sample may also be collected. Rarely, a CSF sample may be collected from the lower back using a procedure called a lumbar puncture or spinal tap.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed

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Common Questions
  • How is it used?

    Beta-2 microglobulin (B2M) test is used as a tumour marker for some blood cell cancers. It is not diagnostic for a specific disease, but it has been associated with the amount of cancer present (tumour burden) and more importantly can give the healthcare professional additional information about someone's likely prognosis. A B2M test may also be requested to help determine the severity and spread (stage) of multiple myeloma and may sometimes be requested to evaluate disease activity and the effectiveness of treatment. Rarely, a CSF B2M test may be requested to assess central nervous system (brain) involvement.

  • When is it requested?

    B2M may be requested during the initial workup of a person who has already been diagnosed with multiple myeloma in order to provide more information on prognosis and may periodically be used to evaluate disease activity and monitor the effectiveness of treatment.

    A CSF B2M may rarely be requested when a healthcare professional suspects that a disease, such as lymphoma, is affecting someone's central nervous system (brain).

  • What does the test result mean?

    Increased amounts of B2M in the blood and/or urine are not diagnostic of a specific disease or condition. They can, however, reflect disease activity and the amount of cancer present, if cancer is the cause of the elevated concentration. When someone has been diagnosed with multiple myeloma or lymphoma, B2M can then be used to assess prognosis with a poorer prognosis associated with high levels of B2M.

    For monitoring treatment, decreasing concentrations over time in someone with multiple myeloma indicate that the person is responding to treatment. Stable or increasing concentrations indicate that the person is not responding.

    Low concentrations of B2M are considered normal and it may be undetectable in the urine and CSF. Elevations of B2M in urine or blood may also indicate renal disease and increases in the CSF in someone with a disease such as HIV/AIDS indicates likely central nervous system involvement.

  • Is there anything else I should know?

    Conditions associated with an increased rate of cell production or destruction, severe infections, viral infections such as CMV (cytomegalovirus), and some conditions that activate the immune system, such as inflammatory conditions and autoimmune disorders, can cause increases in B2M concentrations.

    The kidneys filter B2M from the blood and then reabsorbs it therefore very little B2M should be present in the urine. If the renal tubules in the kidneys become damaged or diseased, less is reabsorbed and concentrations of B2M in the urine increase (see the Beta-2 Microglobulin Kidney Disease test article).

    Drugs such as lithium, ciclosporin, cisplatin, carboplatin, and aminoglycoside antibiotics e.g. gentamicin can increase B2M blood and/or urine concentrations by causing kidney damage primarily.

    Recent nuclear medicine procedures and radiographic contrast media can affect test results.

  • Should everyone have a B2M test?

    Most people will never have a B2M test done. It is not intended, or useful, as a general population screen.

  • Can the test be done in my doctor's surgery?

    Yes, blood and urine samples can be collected for analysis, but it is not routinely performed and the sample may need to be sent to a reference laboratory for analysis

  • Can I choose either a blood or a urine B2M test?

    In most cases, the sample tested will be dictated by the reason that the test is being performed, which is usually a blood sample when B2M is being used as a tumour marker for haematological malignancies e.g. multiple myeloma. In certain neurological situations, cerebrospinal fluid (CSF) may also be tested. The results from urine and blood are not generally interchangeable.

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