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Serum or Plasma Free Light Chain Ratio (kappa to lambda)

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

This test measures the ratio of free kappa and lambda light chains in your blood, which can help diagnose conditions affecting plasma cells, such as multiple myeloma or other monoclonal gammopathies.

Quick summary

["Light chain ratios help identify imbalances linked to blood disorders."]

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

Key facts at a glance

LOINC
77465-3
Short code
Deprecated Hind+Mid ft XR stand
Synonyms
Deprecated Hind+Mid ft XR stand
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
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 Matters for Your Health

Light chains are small protein fragments produced by plasma cells. When these cells become abnormal (e.g., in multiple myeloma), they may release an excess of one type of light chain (kappa or lambda). Measuring both types allows doctors to detect imbalances that may signal disease.

How the Test Works

Blood is drawn and processed to separate free light chains. The test then compares the amounts of kappa and lambda chains, often expressed as a ratio. This ratio helps identify abnormal production patterns.

Common Conditions Monitored

This test is used to screen for or monitor conditions like multiple myeloma, monoclonal gammopathy of undetermined significance (MGUS), and other plasma cell disorders. It may also be used in patients with kidney disease or other conditions affecting protein balance.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic or protein evaluation. Bring any medications you’re currently taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Detecting and Managing Plasma Cell Disorders

Short name

Free Light Chain Ratio

Frequently asked questions

What does a high or low light chain ratio mean?
A high ratio of one type (e.g., kappa) may indicate an excess of that light chain, which can occur in multiple myeloma or other plasma cell diseases. A normal ratio suggests balanced production, but further testing may still be needed to rule out early-stage disease.
Will this test show early signs of multiple myeloma?
Yes, this test can detect imbalances early, even before symptoms appear. However, it’s often used alongside other tests (like serum free light chains or urine protein analysis) for a complete picture.
Can diet or medications affect this test result?
Dietary changes or certain medications (e.g., some chemotherapy drugs) may influence protein levels. Always inform your doctor about all medications or supplements you’re taking 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