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Fatty Acid Profile: Long-Chain Fatty Acid Metabolism Rate (Serum/Plasma)

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

This test measures how efficiently your body converts long-chain fatty acids into usable energy over a 48-hour period. It may be used to assess metabolic function, particularly in conditions affecting fat metabolism or energy production.

Quick summary

["Helps evaluate how well your body processes long-chain fatty acids for energy over time."]

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

Key facts at a glance

LOINC
16855-9
Short code
Fat 48h Stl-mRate
Synonyms
Fat 48h Stl-mRate
Category
chemistry
Sample
stool
Container
Clean container
Units
N/A
Ref low
4.5
Ref high
12
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84436
SNOMED
302345006
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms or conditions related to abnormal fat metabolism, such as unexplained fatigue, muscle weakness, or metabolic disorders. It could also be part of a broader evaluation for genetic or mitochondrial disorders affecting energy production.

What to Expect Before the Test

No special preparation is typically required, but you may be asked to fast for a certain period before the blood draw. Follow your provider’s instructions carefully to ensure accurate results. Avoid consuming high-fat foods if fasting is required.

What the Test Involves

A blood sample will be taken from a vein in your arm. This is a standard procedure that usually causes mild discomfort but should not be painful. The sample is then analyzed to measure the rate at which long-chain fatty acids are metabolized over 48 hours.

What the Results Mean

Results may indicate whether your body is processing long-chain fatty acids efficiently. Abnormal rates could suggest metabolic dysfunction, which may require further testing or medical evaluation to determine the underlying cause.

Reference range

Adult: 4.5-12.0 μg/dLN/A

Specimen: stool

Take your thyroid medication after the blood draw if applicable. No fasting required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Long-chain fatty acid metabolism rate

Frequently asked questions

What does a low or high rate of long-chain fatty acid metabolism mean?
A lower than expected rate might indicate inefficient energy production from fats, which could be linked to metabolic disorders, mitochondrial issues, or genetic conditions. A higher rate may suggest compensatory mechanisms or less efficient fat utilization, though this is less common and would need further investigation.
How often is this test performed?
This test is not routinely performed for general health screening. It is usually ordered as part of a specific diagnostic evaluation for suspected metabolic or energy-related disorders, often in conjunction with other tests.
Can diet or lifestyle changes affect this test result?
Yes, diet—especially high-fat intake—can influence fatty acid metabolism. If fasting was required, avoid eating high-fat foods before the test. Lifestyle factors like physical activity may also play a role, so consistency in preparation is key for accurate results.
  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