Free kappa light chain (serum/plasma, 24-hour urine)

Why This Test Is Done

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

What to Expect Before the Test

For the serum/plasma portion, you’ll typically have a blood draw in a clinic or lab. For the urine portion, you’ll collect all urine over 24 hours in a special container. Drink plenty of fluids to help urine flow normally. Avoid certain medications (like some chemotherapy drugs) that could affect results, but always follow your provider’s specific instructions.

What the Results Mean

High levels of free kappa light chains in either blood or urine may indicate conditions like multiple myeloma, where abnormal plasma cells produce too many light chains. Low or normal levels usually don’t signal a problem unless combined with other findings. Your provider will interpret results in the context of your medical history and other tests.

Common Conditions Monitored

This test is often used to diagnose or track multiple myeloma, Waldenström macroglobulinemia, or other monoclonal gammopathies. It may also help evaluate symptoms like kidney problems (nephropathy) or immune dysfunction linked to plasma cell disorders.