Fatty Acids, Free (Nonester)

Test ID: 


CPT code:



Free Fatty Acids

Nonesterified Free Fatty Acids

Clinical Use:

Free Fatty Acids
Nonesterified Free Fatty Acids

Test Information:

Plasma or serum NEFA is the portion of the total fatty acid pool that circulates in immediate readiness for metabolic needs. NEFA can be absorbed readily by muscle, heart, brain, and other organs as an energy source whenever insufficient quantities of glucose limit the usual carbohydrate energy source. In all probability, both glucose and NEFA are simultaneously taken up from the blood, even under normal conditions. When blood glucose levels are high, the NEFA level falls, and vice versa, emphasizing the reciprocal withdrawal of stored energy, under the simultaneous control of insulin and epinephrine. In acute starvation, the NEFA level may rise as much as three times the normal values.

Specimen Type:

Serum, frozen

Requested Volume: 

1 mL

Minimum Volume: 

0.2 mL

Container Type: 

Red-top tube or gel-barrier tube

Patient Preparation: 

Sample should be collected in the early morning after a 12-hour fast. Blood for the NEFA procedure should be collected after an overnight fast because the level of circulating nonesterified fatty acids is strongly influenced by food ingestion. If the patient has not properly fasted, the determined level of NEFA will be elevated and not directly comparable to a normal range derived from fasting normal controls.


After clotting, separate serum and freeze immediately following centrifugation. Serum is the specimen of choice. Heparin must not be used nor should the patient be on heparin therapy. The NEFA level in serum will increase as it remains at room temperature. Transfer specimen to a plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions:

Freeze. The level of NEFA will increase in serum as it is allowed to stand at room temperature due to enzymatic action.

Stability Requirements:


Rejection Criteria

Heparin plasma received; specimen not frozen. Note: Heparin is known to stimulate the activity of lipoprotein lipase, which acts upon triglycerides associated with blood lipoproteins to release free or nonesterified fatty acids. For this reason, blood collected from patients receiving therapeutic heparin or blood collected in heparinized containers is not suitable for the NEFA test.

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MCI Diagnostic

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Sun: 7AM-3PM

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Sun: 7AM-3PM

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