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Immunoglobulin Heavy Chain Free Light Chain Ratio (Serum)

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

This test measures the ratio of free light chains from immunoglobulin G (IgG) in your blood. It helps assess conditions affecting plasma cells, such as multiple myeloma or other B-cell disorders.

Quick summary

["This ratio helps doctors diagnose and monitor blood disorders linked to abnormal protein production."]

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

Key facts at a glance

LOINC
107199-2
Short code
IgH FR2 Spec
Synonyms
IgH FR2 Spec
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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, bone pain, or kidney problems. It’s also used to monitor treatment progress in conditions like multiple myeloma or lymphoma.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm), and a blood sample will be drawn. The process usually takes a few minutes.

How the Test Results Are Interpreted

Results are compared to a reference range for healthy adults. Abnormal ratios may indicate an overproduction of free light chains, which can signal underlying blood disorders.

Common Conditions Monitored

This test is often used to diagnose or track multiple myeloma, Waldenström macroglobulinemia, or other plasma cell dyscrasias. It may also help evaluate kidney function indirectly.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Free Light Chain Ratio

Frequently asked questions

What does a high or low ratio mean?
A high ratio may suggest conditions like multiple myeloma, where too many free light chains are produced. A low ratio alone is less common but could indicate other immune system issues.
How often will I need this test?
Frequency depends on your condition. If you have a blood disorder, your doctor may order this test periodically to monitor changes in your treatment or disease progression.
Can diet or medications affect this test?
Dietary changes or most over-the-counter medications typically won’t affect this test. However, inform your doctor about any medications, especially those affecting kidney function or immune responses.
  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