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Total Fat-Free Mass (FFM) Rate Over 24 Hours (Serum/Plasma)

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

This test measures how much fat-free body mass (the part of your body that isn’t fat) is being processed or utilized over a 24-hour period, typically using a specialized metabolic assessment.

Quick summary

Assesses overall body composition and metabolic function over time.

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

Key facts at a glance

LOINC
16142-2
Short code
Fat 24h Stl-mRate
Synonyms
Fat 24h Stl-mRate
Category
chemistry
Sample
stool
Container
Clean container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 concerns about muscle loss, metabolic disorders, or how your body uses nutrients. It’s sometimes used in research or specialized clinical settings to evaluate long-term metabolic health.

What to Expect Before the Test

You may need to follow specific dietary or activity restrictions for a few days before testing, as these can affect results. Your provider will guide you on preparation.

How the Test Works

This test involves multiple blood draws over 24 hours to track changes in fat-free mass. A specialized device measures metabolic activity and fluid balance, often using indirect calorimetry or similar technology.

What the Results Mean

Results help determine how efficiently your body maintains or loses fat-free mass. Abnormal findings may indicate metabolic imbalances, muscle wasting, or other conditions requiring further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

24-Hour Fat-Free Mass Rate

Frequently asked questions

How is this test used in clinical practice?
This test is primarily used in research, specialized metabolic studies, or advanced clinical settings (e.g., nutrition, endocrinology) to assess long-term metabolic health, muscle preservation, or body composition changes. It’s not a standard diagnostic test for most routine medical conditions.
What does a low/high result indicate?
A lower-than-expected rate may suggest muscle loss, poor metabolic function, or conditions like malnutrition or certain metabolic disorders. A higher-than-expected rate could indicate unusual metabolic activity or overutilization of body mass, though this is less common and would require further evaluation.
How often is this test repeated?
This test is typically performed once, as it requires a full 24-hour monitoring period. Results are compared to baseline or reference ranges specific to the study or clinical context, not general population norms.
  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