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Serum or plasma free light chain kappa to lambda ratio (immunoassay)

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 identify certain blood disorders.

Quick summary

["Light chain imbalance may signal multiple myeloma or other conditions affecting plasma cells."]

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

Key facts at a glance

LOINC
93788-8
Short code
F5 HR2 Geno Bld
Synonyms
F5 HR2 Geno Bld
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
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 kidney problems. It’s also used to monitor conditions like multiple myeloma, where abnormal plasma cells produce excess light chains.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. If you’re on blood thinners, let your doctor know before the test.

What the Test Results Mean

A normal ratio suggests balanced light chains. An elevated ratio may indicate overproduction of kappa chains (common in multiple myeloma), while a low ratio may suggest lambda dominance. Results are interpreted by your doctor in the context of your symptoms and medical history.

Common Conditions Monitored

This test helps diagnose or track multiple myeloma, plasma cell leukemia, or other plasma cell dyscrasias. It may also be used in patients with kidney disease or autoimmune conditions linked to light chain abnormalities.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Light Chain Ratio

Frequently asked questions

What causes an abnormal light chain ratio?
Abnormal ratios are most commonly linked to multiple myeloma, where plasma cells produce too many kappa or lambda chains. Other causes may include plasma cell leukemia, Waldenström macroglobulinemia, or certain autoimmune diseases. Kidney disease or medications that affect light chain clearance can also influence results.
How is this test different from a complete blood count (CBC)?
A CBC checks overall blood cell counts (red cells, white cells, platelets), while this test focuses specifically on the ratio of free kappa and lambda light chains. Both are important—your doctor may order both if you have symptoms of blood disorders.
Can diet or medications affect this test?
Dietary changes or most over-the-counter medications typically don’t affect light chain ratios. However, if you’re on medications like chemotherapy, steroids, or blood pressure drugs, inform your doctor before testing, as they may influence results or your condition’s management.
  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