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Plasma or Serum Creatinine Concentration (Mass Concentration)

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

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

Quick summary

["Kidney function is often checked with this test to detect early kidney damage."]

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

Key facts at a glance

LOINC
9903-6
Short code
P wave dur L-AVR
Synonyms
P wave dur L-AVR
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 Your Kidneys Matter

Your kidneys filter waste and excess substances from your blood, including creatinine. If your kidneys aren’t working well, creatinine levels can rise in your blood. This test helps doctors monitor kidney health, especially if you have conditions like diabetes, high blood pressure, or a family history of kidney disease.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw (from a vein) or a urine sample collected. If you’re on a diet low in meat or protein, your doctor may advise you to avoid it for a few days before testing to get a more accurate result.

How the Test Works

Blood or urine is sent to a lab where it’s analyzed to measure creatinine levels. Blood tests are typically done using an automated method that separates blood components and measures the substance’s concentration.

What Your Results Mean

Higher than expected creatinine levels may indicate reduced kidney function, while lower levels could suggest overhydration or muscle breakdown. Your doctor will compare your results to your health history and other tests to interpret them correctly.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

What could cause my creatinine levels to be higher than usual?
Higher creatinine levels may be due to kidney disease, dehydration, muscle disorders, or certain medications. If you notice symptoms like swelling, fatigue, or changes in urine, talk to your doctor—these could signal kidney problems.
Could my diet affect this test?
Yes, eating a high-protein diet before testing may temporarily raise creatinine levels. If your doctor ordered this test, they may have given you specific instructions about diet or timing to get the most accurate result.
Why do doctors check creatinine levels regularly?
Regular creatinine checks help monitor kidney health, especially in people with conditions like diabetes or high blood pressure. It’s also useful for tracking how well treatments are working or detecting early signs of kidney damage.
  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