Serum or Plasma Free Light Chain Immunoglobulin (Free Kappa and Lambda Light Chains)

Why This Test Is Done

Your healthcare provider may order this test to investigate symptoms such as fatigue, weight loss, or unexplained infections. It can also help diagnose conditions like multiple myeloma, lymphoma, or other plasma cell disorders. Sometimes, it’s used alongside other tests to monitor treatment progress or detect early signs of disease.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re on blood thinners, let your provider know before the test. Avoid eating or drinking for 2–4 hours before if instructed, but this isn’t always required.

What the Test Results Mean

Free light chains are normally balanced in your blood, with roughly equal amounts of kappa and lambda. If one type is significantly elevated, it may indicate a problem with plasma cells, such as multiple myeloma or other cancers. Your provider will compare results to your symptoms and other tests for a full picture.

Common Conditions Linked to Abnormal Results

High levels of free light chains are often linked to plasma cell disorders (e.g., multiple myeloma), lymphoma, or other cancers affecting the bone marrow. They can also appear in conditions like chronic infections or certain autoimmune diseases. Low levels alone are less common but may signal other immune or blood-related issues.