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Test Code FATTYA Free Fatty Acids, Total, Serum

Reporting Name

Free Fatty Acids, Total, S

Useful For

Evaluation of metabolic status of persons with endocrinopathies


Detection of pheochromocytoma and of glucagon-, thyrotropin-, and adrenocorticotropin-secreting tumors


Monitoring of control of diabetes mellitus (serum-free glycerol is a very useful companion test in assessing diabetes and may be ordered by special request from Mayo Medical Laboratories). The correlation with insulin resistance and downstream cardiovascular risk may be a useful treatment aid in some patients.

Seattle Children's Hospital Note:


Non-esterified fatty acids (NEFA)

Specimen Required

Patient Preparation:

1. Fasting-overnight (12-14 hours).

2. Patient must not consume any alcohol for 24 hours before the specimen is drawn.

Collection Container/Tube: 

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Spin down within 45 minutes of draw.

2. Immediately freeze specimen.

Seattle Children's Hospital Note:

Collect 2.0 mL whole blood in a Red top.

Specimen Type


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen

Day(s) and Time(s) Performed

Monday through Friday; 7 a.m.-5 p.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Method Name

Enzymatic Colorimetric

Method Description

Unesterified (free) fatty acids are measured by direct analysis of serum. Serum free fatty acids react with CoA in the presence of ATP, Mg(++), and acyl-CoA synthetase to form thiol esters of CoA. The esters are oxidized by acyl-CoA oxidase to produce hydrogen peroxide, which reacts with a signal compound to produce purple adduct. The free fatty acid concentration is proportional to the absorbance at 550 nm. Ascorbate oxidase is included as a reagent to completely remove any ascorbic acid in the specimen, which would interfere with the oxidative reactions.(Unpublished Mayo method)

Reference Values

≥16 years: 0.00-0.72 mmol/L

Reference values have not been established for patients who are <16 years of age.

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
NEFA Free Fatty Acids, Total, S 15066-4


Result ID Test Result Name Result LOINC Value
NEFA Free Fatty Acids, Total, S 15066-4

Reject Due To


Mild OK; Gross reject


Mild OK; Gross reject


Mild OK; Gross reject




If not ordering electronically, complete, print, and send a Cardiovascular Test Request Form (T724) with the specimen (