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Serum or Plasma Free Light Chain Immunoassay (Quantitative)

Published: August 9, 2026Updated: August 16, 2026

This test measures the levels of free light chains (kappa and lambda) in your blood, which are protein fragments produced by plasma cells. It helps diagnose conditions affecting the bone marrow or immune system.

Quick summary

["This test helps identify certain blood disorders by detecting abnormal light chains that may indicate multiple myeloma or other plasma cell diseases."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
63315-6
Short code
RF IgM Fld IA-aCnc
Synonyms
RF IgM Fld IA-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
86430
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

Why This Test Is Done

Your doctor may order this test if you have symptoms like unexplained fatigue, bone pain, frequent infections, or kidney problems. It’s also used to monitor treatment progress for conditions like multiple myeloma or other plasma cell disorders.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re on blood thinners, let your doctor know before the test.

What the Test Results Mean

Results show the amount of kappa and lambda light chains separately. Elevated levels of one type (usually lambda) may suggest a plasma cell disorder. Your doctor will interpret results in the context of your symptoms and other tests.

Common Conditions Monitored

This test is primarily used to diagnose or monitor multiple myeloma, Waldenström macroglobulinemia, and other plasma cell dyscrasias. It can also help assess kidney function indirectly by detecting light chains that may filter into urine.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Light Chain Test

Frequently asked questions

What does a high or low light chain level mean?
A high level of one type (usually lambda) is often linked to plasma cell disorders like multiple myeloma. Low levels alone are usually not clinically significant unless part of a broader evaluation.
How often will I need this test?
Your doctor will determine the frequency based on your condition and treatment plan. Some patients need it monthly, while others may only need it yearly or as needed.
Can diet or medications affect this test?
Dietary changes or most over-the-counter medications typically do not affect light chain levels. However, long-term steroid use or certain chemotherapy drugs may influence results, so discuss this with your doctor.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy