Serum or Plasma Free Light Chain Immunoassay (Free Light Chain Immunoglobulin Profile)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like unexplained fatigue, frequent infections, bone pain, or kidney problems. It may also be used to monitor conditions like multiple myeloma, lymphoma, or other immune system disorders. Sometimes, it’s part of a broader evaluation for unexplained abnormalities in blood tests.

What to Expect Before the Test

You’ll typically have a small needle inserted into your arm or vein to draw blood. No special preparation is needed, but avoid eating or drinking for a few hours before the test if instructed. If you’re on blood thinners, let your provider know before the test.

What the Test Results Mean

Free light chains are normally present in small amounts in the blood. Abnormal levels—either too high or too low—can signal underlying health issues. Your results will be compared to a reference range provided by your lab, and your provider will discuss them with you.

Common Conditions Monitored

This test is often used to diagnose or track conditions like multiple myeloma (a cancer of plasma cells), Waldenström macroglobulinemia (a rare blood cancer), or other disorders affecting antibody production. It can also help identify kidney problems linked to abnormal antibody fragments.