Test guide
Free Light Chains
A free light chains test measures the level of free light chains in your blood. Light chains are proteins made by plasma cells, a type of white blood cell. Light chains usually link up with other proteins called heavy chains. Together, the light and heavy chains make immunoglobulins, also called antibodies. Antibodies are proteins that your immune system makes to fight germs such as viruses and bacteria .
What it is for
A free light chains test is used to measure the level of free light chains in the blood and compare the amount of kappa and lambda light chains. This ratio can help diagnose or monitor how well the treatment of plasma cell disorders is working. Source: MedlinePlus, National Library of Medicine. Medical test information is public domain. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Limitations
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
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