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How is Multiple Myeloma Diagnosed?

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Last updated and reviewed on: July 28, 2026

Multiple myeloma is a type of blood cancer that affects plasma cells. If your doctor thinks you may have multiple myeloma, there are tests and procedures that can confirm a diagnosis. 

A single test result is not enough to diagnose multiple myeloma. Diagnosis relies on a combination of factors, including your symptoms, a physical examination by your doctor, and the results of multiple tests. 

This page lists all of the different tests that may be needed. Some are used to confirm a multiple myeloma diagnosis. Others are used to learn more about the cancer, such as genetic mutations, that can help guide treatment. Others are used to monitor how well treatment is working. You may not have all of the tests on this list.

Talk to your care team if you have questions about the type of tests you received and what the results mean for your diagnosis. 

How is multiple myeloma diagnosed?

To confirm a multiple myeloma diagnosis, you must have one of the following:

  • A plasma cell tumor confirmed by biopsy

  • More than 10% plasma cells in the bone marrow

And any one or more of the SLiM CRAB features of myeloma:

  • Hypercalcemia

  • Renal (kidney) problems

  • Anemia

  • Bone lesions

  • 60% or greater clonal plasma cells in the bone marrow

  • Serum involved/uninvolved free light chain ratio of 100 or greater

  • More than one focal lesion on MRI that is at least 5mm or greater

Blood and urine tests used to diagnose multiple myeloma

Blood tests

Routine blood tests such as a complete blood count will be done during diagnosis and throughout myeloma treatment. 

Complete blood count (CBC). This test measures your red cells, white cells, and platelets. If myeloma cells are crowding out your bone marrow, you may have anemia (low red blood cells) and low counts of white cells and platelets.

Blood tests to measure kidney function. Your blood urea nitrogen (BUN) and creatinine will be measured to test kidney function.

Other blood tests. You may need tests to measure: 

  • Albumin

  • Calcium

  • Lactic dehydrogenase (LDH)

  • Beta-2 microglobulin (B2M)

These can help determine the stage of myeloma.

Minimal residual disease (MRD) tests

MRD tests measure small amounts of myeloma cells in the blood. It is used to know how well treatment is working to treat myeloma.

Tests to find M proteins

Most people with multiple myeloma and other plasma cell disorders have signs of M proteins. 

The tests find different parts of the M proteins. 

M proteins are Y-shaped. Each part of the Y is made up of pieces called chains. Some chains are heavy, and others are light. There are different types of heavy and light chains.

Heavy chains found in M proteins:

  • IgG

  • IgA

  • IgD

  • IgM

  • IgE

IgG heavy chains are the most common. About 65% of people with myeloma have IgG myeloma. IgA heavy chains are the second-most common type. IgD, IgM, and IgE myeloma are more rare. 

Light chains found in M proteins: 

  • Kappa

  • Lamda 

About half of people with myeloma have free light chains in the bloodstream. About 20% of people with myeloma only have light chains and no heavy chains. Learn more about light-chain only myeloma.

The blood and urine tests to find M proteins at diagnosis and throughout treatment include:

Serum protein electrophoresis (SPEP). This test detects M protein in the blood. It also measures the size of the M protein. It is usually done in combination with a test called serum immunofixation. 

Serum immunofixation. This test also measures M protein in the blood. It is more sensitive than SPEP and can find the type of heavy and light chains in the M protein. But it can’t measure the size of the M protein. SPEP and serum immunofixation can be done together to get a complete understanding. 

Urine protein electrophoresis (UPEP). For this test, urine is collected over 24 hours in a special container. It measures the total amount of protein found in the urine during the day. When light chains are found in the urine, they are called Bence Jones protein.

Urine immunofixation. This is another test that is used to measure m protein in the urine. It is more sensitive than UPEP and can find the type of heavy and light chains in the M protein, but it can’t measure the size of the M protein. That is why it is done with UPEP. 

Serum free light-chain and serum heavy/light-chain assay. A serum free light-chain assay measures the amount of light chains in the blood. A serum free heavy/light-chain assay measures the isotypes, or combinations of heavy and light chains that make up the M proteins.

Bone marrow aspiration and biopsy to diagnose multiple myeloma

A bone marrow aspiration and biopsy is an important test to see if myeloma cells are present in the bone marrow. This procedure uses a needle to extract a small sample of bone and marrow (biopsy) or bone marrow (aspiration). It is typically taken from the pelvic bone. While it may cause brief discomfort, it is usually done with local anesthesia or light sedation. 

Imaging tests to diagnose multiple myeloma

Imaging tests are an important part of a multiple myeloma diagnosis. Different imaging tests that are used to diagnose multiple myeloma and monitor bone damage. These include:

  • Computed tomography (CT) scans

  • Magnetic resonance imaging (MRI) 

  • Positron emission tomography (PET) 

  • X-rays

Other tests 

Fluorescence in situ hybridization (FISH). This test is used to find genetic abnormalities and help predict prognosis. 

What’s Next: The next page in this guide is Understanding Multiple Myeloma Lab Results. If you would like to read another page in this guide, return to the Understanding Multiple Myeloma page or choose another page from the menu.

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