MGUS is usually detected during blood tests for another condition, such as a certain nerve disorder (peripheral neuropathy). The blood tests can show abnormal proteins as well as unusual amounts of normal proteins.

If your doctor detects monoclonal gammopathy, further testing may be recommended to determine which M protein your body is making and how much is being made.

To rule out other causes of elevated protein levels, your doctor might recommend:

  • Additional blood tests. Tests to count the blood cells in your blood (complete blood count), to look for a decline in kidney function (serum creatinine test) and to determine the amount of calcium in your blood (serum calcium test) can help rule out conditions such as multiple myeloma.
  • Urine tests. These tests can determine if abnormal protein is being released into your urine, and assess any resulting kidney damage. You'll likely need to collect your urine for 24 hours.
  • Imaging tests. If you are experiencing bone pain, your doctor might recommend an MRI or CT-positron emission tomography (PET) scan. The images can help your doctor find bone abnormalities related to MGUS.
  • Bone marrow test. A hollow needle removes a portion of your bone marrow from the back of one of your hipbones. The bone marrow is analyzed to determine its percentage of plasma cells. Bone marrow testing is generally done only when you're at risk of developing a more serious disease or if you have unexplained anemia, kidney failure, bone lesions or high calcium levels.