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Serum or plasma free light chain assay (total)

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

This test measures the levels of free light chains—small protein fragments released when antibodies break down. It helps evaluate conditions affecting plasma cells, such as multiple myeloma or certain autoimmune diseases.

Quick summary

["Assessing abnormal antibody production or related blood disorders."]

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

Key facts at a glance

LOINC
34685-8
Short code
PT imm FX DP PPP
Synonyms
PT imm FX DP PPP
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
coag-tissue-factor-induced-factor-substitution-immediately-after-addition-of-factor-x-depleted-plasma
CPT
85610
SNOMED
396252006
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

Free light chains are part of antibodies, which your immune system uses to fight infections. When plasma cells (a type of white blood cell) become overactive or malfunction, they may produce too many light chains. This test helps doctors detect imbalances that could signal conditions like multiple myeloma, lymphoma, or other blood disorders.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample (either serum or plasma) via a simple venipuncture. If you’re on blood thinners, let your provider know before the test.

Common Conditions Monitored

This test is often used to monitor plasma cell disorders, including multiple myeloma (a cancer of plasma cells), Waldenström macroglobulinemia (a rare blood cancer), and certain autoimmune diseases like systemic lupus erythematosus or rheumatoid arthritis.

How Results Are Used

Doctors use these results to diagnose or track conditions affecting antibody production. Elevated levels may indicate overactive plasma cells, while abnormal ratios (between kappa and lambda chains) can help confirm specific disorders.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: plasma

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Total Free Light Chains

Frequently asked questions

What does a high or low result mean?
High levels of free light chains may suggest plasma cell disorders, kidney issues (since kidneys filter these proteins), or certain infections. Low levels alone are less meaningful but could indicate immune system dysfunction in rare cases. Always discuss results with your healthcare provider, as they’ll consider your full medical picture.
Will this test affect my medications?
No, this test does not directly interact with most medications. However, if you’re on blood thinners (e.g., warfarin), let your provider know to avoid unnecessary delays in testing.
How often should I get this test?
Frequency depends on your condition. For example, patients with multiple myeloma may need regular monitoring, while others with autoimmune diseases might get it less often. Follow your doctor’s recommendations.
  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