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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 key indicator of kidney function and overall kidney health."]

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

Key facts at a glance

LOINC
9958-0
Short code
QRS dur L-V4
Synonyms
QRS dur L-V4
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 play a vital role in filtering waste products, including creatinine, from your blood. This test helps doctors check if your kidneys are working properly by measuring how well they remove creatinine from your bloodstream.

What Creatinine Does in Your Body

Creatinine is a byproduct of muscle activity. When your kidneys filter blood, they remove creatinine and send it to your bladder for excretion. High levels in your blood can signal impaired kidney function.

How This Test Works

Blood is drawn and sent to a lab, where it is analyzed to determine the concentration of creatinine. The results help doctors compare it to what’s expected for your body size and health.

What Normal Results Mean

Normal results typically indicate that your kidneys are functioning well. However, individual results can vary based on factors like age, sex, and muscle mass. Your doctor will interpret the results in relation to your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Kidney Function and Health Monitoring

Short name

Creatinine Level

Frequently asked questions

Why might my doctor order this test?
Your doctor may order this test to check for kidney problems, monitor chronic conditions like diabetes or high blood pressure, or evaluate symptoms such as swelling, fatigue, or changes in urine output. It’s also used before surgeries or treatments that may affect kidney function.
What does a high creatinine level mean?
A high creatinine level often suggests that your kidneys are not working as well as they should. This can indicate kidney disease, where the kidneys struggle to filter waste products efficiently. It’s important to discuss any concerns with your doctor, as they may recommend further tests or adjustments to your treatment plan.
What if my creatinine level is low?
A low creatinine level might suggest that your kidneys are working better than average, but it can also be influenced by factors like low muscle mass or certain medical conditions. Your doctor will consider all your health information to understand the cause and next steps.
  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