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Serum or plasma concentration of free fatty acids (specifically long-chain fatty acids)

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

This test measures the levels of certain long-chain fatty acids in your blood, which can help assess fat metabolism and energy production.

Quick summary

["Long-chain fatty acids play a key role in energy and cell function—abnormal levels may signal metabolic or health concerns."]

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

Key facts at a glance

LOINC
71359-4
Short code
Y chr AZFa region Del Bld/T
Synonyms
Y chr AZFa region Del Bld/T
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like fatigue, muscle weakness, or unexplained weight changes, especially if they suspect conditions like mitochondrial disorders, fatty acid oxidation defects, or metabolic syndrome. It may also be used in research or specialized diagnostic evaluations.

What to Expect Before the Test

No special preparation is typically needed, but you may be asked to fast for 8–12 hours before drawing blood to ensure accurate results. Avoid heavy meals or alcohol before testing.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results show the concentration of specific long-chain fatty acids in your blood. While reference ranges vary by lab, abnormal levels may indicate metabolic issues or other health conditions that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free fatty acid profile

Frequently asked questions

How long does it take to get results?
Results are usually available within 1–3 business days, depending on lab processing times. Your healthcare provider will discuss findings with you during your follow-up visit.
What causes abnormal fatty acid levels?
Abnormal levels may result from genetic disorders (e.g., fatty acid oxidation defects), liver disease, malnutrition, or certain medications. Symptoms like fatigue or muscle pain often prompt testing.
Can diet affect this test?
Yes, diet can influence results. Fasting for 8–12 hours before testing helps standardize measurements. Avoid high-fat meals or supplements that may alter fatty acid profiles.
  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