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Free Serum Creatinine (Mass Concentration)

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

This test measures the amount of creatinine, a waste product from muscle metabolism, in your serum (blood plasma without clotting factors) in its free, unbound form. Creatinine is a key indicator of kidney function.

Quick summary

["Your kidneys filter creatinine; high levels may signal impaired kidney function."]

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

Key facts at a glance

LOINC
46972-6
Short code
Deprecated 6MAM Free SerPl Cfm-mCnc
Synonyms
Deprecated 6MAM Free SerPl Cfm-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
confirm
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test to evaluate kidney health, monitor chronic kidney disease, or assess kidney function in people with conditions like diabetes or hypertension. It can also help diagnose or track kidney-related issues, such as acute kidney injury or certain metabolic disorders.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into a vein (usually in your arm) to draw blood. If you’re on a blood thinner, inform your healthcare provider beforehand. Avoid strenuous activity or eating/drinking for 8–12 hours before if instructed.

What the Test Results Mean

Results are compared to a general reference range (not provided here) to determine if your kidney function is normal or if further action is needed. Elevated levels may suggest kidney problems, while very low levels could indicate muscle breakdown or other metabolic issues.

Common Conditions Affecting Results

Kidney disease, dehydration, severe muscle disorders, or certain medications (like NSAIDs) can alter creatinine levels. Conditions like liver disease or heart failure may also impact how creatinine is processed in the body.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Serum Creatinine

Frequently asked questions

Why might my doctor request this test?
Your doctor may ask for this test to check if your kidneys are working properly, especially if you have symptoms like fatigue, swelling, or changes in urine output. It can also help monitor kidney health during treatments or if you have conditions that affect metabolism.
What does a high or low result mean?
A high result may indicate poor kidney function or reduced blood flow to the kidneys. A low result could suggest muscle wasting, liver disease, or dehydration. Always discuss results with your healthcare provider—they’ll interpret them in the context of your overall health.
Can diet or medications affect this test?
Yes. High-protein diets or muscle-building exercises can temporarily raise creatinine levels. Some medications (like certain diuretics or contrast dyes used in imaging) may also impact results. Avoid these factors for a few days before testing if possible.
  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