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Serum/plasma free light chain kappa to lambda ratio (FLC ratio)

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

This test measures the balance between two types of light chains—kappa and lambda—that are released by your immune system’s B cells. It helps assess conditions affecting plasma cells, such as multiple myeloma or other monoclonal gammopathies.

Quick summary

["A ratio imbalance may signal an underlying blood disorder requiring further evaluation."]

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

Key facts at a glance

LOINC
47929-5
Short code
GH sp6 p chal SerPl-aCnc
Synonyms
GH sp6 p chal SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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, frequent infections, or unexplained bone pain. It’s also used in monitoring multiple myeloma, lymphoma, or other conditions where abnormal protein production occurs.

How the Test Works

A blood sample is drawn, and the test measures the free kappa and lambda light chains separately. The ratio of these two components is then calculated to identify any imbalances.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any medications or conditions that could affect results, such as kidney disease or recent infections.

Possible Results and Next Steps

A normal ratio suggests balanced light chain production, while an elevated or low ratio may indicate a condition like multiple myeloma or other plasma cell disorders. Your doctor will discuss results with you and may recommend additional tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Understanding the Role of Free Light Chains

Short name

Free Light Chain Ratio

Frequently asked questions

What does an abnormal FLC ratio mean?
An abnormal ratio (either elevated or low) may signal an overproduction of one type of light chain, often linked to conditions like multiple myeloma, lymphoma, or monoclonal gammopathy of unknown significance (MGUS). These conditions can affect kidney function and cause symptoms like bone pain or anemia.
How often should this test be repeated?
If you have a known condition like multiple myeloma, your doctor may order this test regularly to monitor disease progression or response to treatment. Frequency depends on your specific diagnosis and treatment plan.
Can diet or medications affect this test?
Certain medications (e.g., chemotherapy) or kidney disease may influence light chain levels, but diet alone typically does not affect this test. Always discuss your medications and health status with your doctor before the test.
  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