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Serum or Plasma Creatinine (Creatinine Concentration)

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

This test measures the level of creatinine, a waste product from muscle metabolism, in your blood or plasma. It helps assess how well your kidneys are filtering blood.

Quick summary

["A creatinine test helps evaluate kidney function and detect early kidney problems."]

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

Key facts at a glance

LOINC
93635-1
Short code
RA ES vol A4C
Synonyms
RA ES vol A4C
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-d-a-c
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 Matters

Your kidneys normally filter waste products, including creatinine, from your blood. High levels of creatinine can indicate reduced kidney function or damage. This test is often used alongside other measures, like blood urea nitrogen (BUN), to assess kidney health.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to avoid certain medications or foods for a short time if directed by your healthcare provider. If you have a recent meal, drink plenty of fluids before the test to help your kidneys process waste products normally.

How the Test Is Done

A healthcare professional will draw blood from a vein in your arm using a small needle. The blood sample is then sent to a lab for analysis. If you have a urine test for creatinine clearance, you may be asked to collect a 24-hour urine sample instead.

What the Results Mean

Results are compared to a reference range that varies by lab and age. High creatinine levels may suggest kidney problems, while very low levels might indicate dehydration or muscle disorders. Your doctor will interpret the results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine

Frequently asked questions

What causes elevated creatinine levels?
Elevated creatinine levels can be caused by kidney disease, dehydration, severe muscle injury, or conditions that reduce blood flow to the kidneys. Chronic kidney disease (CKD) is a common reason for higher creatinine, as it impairs the kidneys' ability to filter waste properly.
What causes low creatinine levels?
Low creatinine levels may occur if you have very little muscle mass, severe malnutrition, or conditions that affect muscle metabolism. Rarely, it can also be seen in certain genetic disorders or during pregnancy.
Can creatinine levels change over time?
Yes, creatinine levels can fluctuate due to changes in kidney function, hydration status, muscle activity, or medications. Regular monitoring is important for people with chronic kidney conditions or those taking medications that affect kidney function.
  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