Serum or Plasma Free Light Chain Immunoassay (κ or λ)
This test measures the free light chains (κ or λ) in your blood, which are small protein fragments produced by plasma cells. These fragments can help identify conditions affecting the immune system or bone marrow.
["Free light chains help diagnose and monitor conditions like multiple myeloma or other plasma cell disorders."]
Key facts at a glance
- LOINC
- 34446-5
- Short code
- RBC Fld Ql
- Synonyms
- RBC Fld Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Is a Free Light Chain Test Used For?
Free light chains are part of the heavy and light chains produced by plasma cells. When plasma cells are healthy, they balance the production of both κ (kappa) and λ (lambda) light chains. However, in diseases like multiple myeloma, plasma cells may overproduce one type of light chain, leading to an imbalance. This test helps detect and monitor these imbalances by measuring the free κ or λ light chains in your blood. It can also assist in diagnosing conditions such as amyloidosis or other immune system disorders.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum or plasma, where the free light chains are measured using an immunoassay method. This test is typically done on the same day as the blood is drawn.
Why Might You Need This Test?
Your healthcare provider may recommend a free light chain test if you have symptoms or risk factors for conditions like multiple myeloma, such as unexplained fatigue, bone pain, frequent infections, or kidney problems. It may also be used to monitor the progression or response to treatment in these conditions.
What Do the Results Mean?
Results are usually reported as absolute values for κ and λ light chains. Elevated levels of one type of light chain compared to the other may indicate an underlying condition affecting plasma cells. Your healthcare provider will interpret the results in the context of your overall health and symptoms.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Free Light Chain Test
Frequently asked questions
How often will I need this test?
What are the possible side effects of having this test?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy