Skip to content

Serum or Plasma Creatinine Concentration (Substance 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 plasma. It helps assess how well your kidneys are filtering blood.

Quick summary

["A creatinine test helps check kidney function by measuring how well your kidneys remove waste from your blood."]

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

Key facts at a glance

LOINC
31920-2
Short code
N men sg W135 Ag Spec Ql
Synonyms
N men sg W135 Ag Spec Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

Creatinine levels can indicate how efficiently your kidneys are working. High levels may suggest kidney damage or disease, while low levels could signal dehydration or other conditions affecting fluid balance.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw from a vein in your arm, or a urine sample may be collected if testing creatinine clearance. If you’re on a low-protein diet, discuss it with your healthcare provider before testing.

Common Causes of Abnormal Results

Elevated creatinine levels might be due to kidney disease, dehydration, severe muscle damage, or conditions that reduce blood flow to the kidneys. Low levels could result from dehydration, overhydration, or certain medications.

When You Might Need This Test

Your doctor may order this test to monitor kidney health before or after treatments, check for kidney problems, evaluate symptoms like fatigue, swelling, or changes in urine, or assess overall health during chronic illnesses.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

How often should I get this test?
Your doctor will determine the frequency based on your health status, medications, and any kidney-related conditions. Regular monitoring may be needed if you have diabetes, high blood pressure, or a history of kidney issues.
What do my results mean if they’re out of range?
Results are interpreted by your healthcare provider in relation to your overall health. High levels may signal kidney problems, while low levels could indicate dehydration or other factors. They won’t stand alone—your provider will consider other factors like symptoms and medical history.
Can diet affect this test?
Yes, diet can influence creatinine levels. High-protein foods may temporarily increase creatinine, while dehydration can lower it. Your doctor may recommend dietary adjustments or timing your test around meals if needed.
  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