Free kappa to lambda ratio calculator
Compares kappa with lambda free light chains. A lopsided ratio can be a clue to a plasma cell condition, but kidney disease also shifts it. Type your results in the units on your report and it works out Kappa/lambda ratio as you type, in your browser.
AI-verified against cited sources. Awaiting expert reviewLast reviewed 2026-10-03Cancer Markers
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Educational information, not medical advice. Blood Test Tracker doesn’t diagnose or treat, and it doesn’t replace your clinician. Talk with your clinician before changing medications, supplements or care.
How it’s worked out
The formula
Free kappa light chains (mg/L) ÷ free lambda light chains (mg/L). Both values must come from the same sample and assay and be in the same unit. The unit cancels, so the ratio is the same number in mg/L and mg/dL.
A worked example
Example numbers, not anyone’s real results, run through the same code as the calculator above.
| Free kappa | 12 mg/L |
|---|---|
| Free lambda | 15 mg/L |
| Kappa/lambda ratio | 0.80 ratio |
For an adult, this result is in the usual range.
What Kappa/lambda ratio tells you
The kappa/lambda ratio is the free kappa result divided by the free lambda result. In healthy people the two types are made in a steady balance, so the ratio stays inside a fairly narrow range. When one clone of plasma cells makes too much of one type, the ratio tips. Your lab calculates it from the two free light chain results, and it is usually printed right below them.
The ratio is the key number on a free light chain test. It is more telling than either chain alone, because reduced kidney function raises both chains together and moves the ratio only a little. Clinicians use it with protein electrophoresis and immunofixation to look into monoclonal gammopathy (MGUS), multiple myeloma and light chain (AL) amyloidosis, and to follow people who have them. A ratio outside the range is not a diagnosis, and it is common in people with reduced kidney function. In a large Icelandic study of people with an eGFR below 60, 9% had a ratio outside the standard range, but fewer than 1% had light chain MGUS. For myeloma, the International Myeloma Working Group counts an involved-to-uninvolved ratio of 100 or more, with the involved chain at 100 mg/L or more, as a myeloma-defining finding.
Read the full page on Kappa/lambda ratio, with what a high or low result can mean.
Usual ranges
The ranges the result above is placed on. Your own lab’s printed range comes first if it gives one.
- Adults0.26–1.65 ratio
Sources: Clinical Chemistry, ARUP Laboratories, University of Iowa Hospitals & Clinics Pathology Handbook, Mayo Clinic Laboratories (Extended Catalog), Biochemia Medica, Blood
- ckd0.37–3.1 ratio
Sources: Clinical Journal of the American Society of Nephrology, Blood Cancer Journal
Sources
The equation
- Immunoglobulin Free Light Chains, Serum (test FLCS), Mayo Clinic Laboratories (Extended Catalog)
- Kappa/Lambda Quantitative Free Light Chains with Ratio, Serum (test 0055167), ARUP Laboratories
11 more sources for the ranges and the explanation
- Serum reference intervals and diagnostic ranges for free kappa and free lambda immunoglobulin light chains: relative sensitivity for detection of monoclonal light chains, Clinical Chemistry (2002)
- Kappa-Lambda Quant Free Light Chain Ratio, Blood, University of Iowa Hospitals & Clinics Pathology Handbook
- Comparison of Freelite and N-Latex serum free light chain assays: a critical review, Biochemia Medica (2021)
- Quantitative assessment of serum and urinary polyclonal free light chains in patients with chronic kidney disease, Clinical Journal of the American Society of Nephrology (2008)
- Defining new reference intervals for serum free light chains in individuals with chronic kidney disease: Results of the iStopMM study, Blood Cancer Journal (2022)
- International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders, Leukemia (2009)
- International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma, The Lancet Oncology (2014)
- Serum free light chains in a racially diverse population including African Americans and populations from South Africa, Blood (2025)
- Extracorporeal Free-Light-Chain Removal in Myeloma Cast Nephropathy: Plasma Exchange and Hemodialysis Strategies in the Era of Effective Antimyeloma Therapy, Journal of Clinical Medicine (2026)
- Elevated serum polyclonal immunoglobulin free light chains in patients with severe asthma, Frontiers in Pharmacology (2023)
- Diagnostic and Therapeutic Aspects of Monoclonal Gammopathies of Renal Significance (MGRS): An Update, Diagnostics (Basel) (2024)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. The calculator is version 1.0.0 of our code for this equation, tested against published examples. How we build and check these pages.