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Serum or Plasma Creatinine Concentration (Standard Method)

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

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

Quick summary

["Kidney function check with a simple blood test."]

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

Key facts at a glance

LOINC
9959-8
Short code
QRS dur L-V5
Synonyms
QRS dur L-V5
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

Creatinine is a byproduct of muscle metabolism that your kidneys filter out of your blood. High levels can signal kidney problems, even if you don’t have symptoms yet. This test is often used alongside other measures to monitor kidney health, especially in people with diabetes, high blood pressure, or a family history of kidney disease.

What the Test Shows

Your results compare to a general reference range for healthy adults. While exact values can vary by lab, consistently high or low readings may prompt further evaluation. Some factors, like diet, muscle mass, or hydration status, can temporarily affect results.

How It’s Done

A simple blood sample is taken from your arm. If testing urine creatinine is needed, you’ll collect a sample over 24 hours. No special preparation is usually required, but your doctor may advise avoiding certain foods or drinks before testing.

Common Reasons for Testing

Doctors order creatinine tests to check for kidney disease, track chronic conditions like diabetes or heart disease, evaluate dehydration, or monitor treatment effects. It’s also used in some medical emergencies, like severe infections or injuries.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Creatinine

Frequently asked questions

What does a high creatinine level mean?
High creatinine levels may indicate reduced kidney function, though other conditions (like muscle disorders or dehydration) could also cause them. Your doctor will consider your overall health and other test results to interpret results accurately.
What if my creatinine level is low?
Low creatinine levels might suggest you have less muscle mass, severe malnutrition, or very low kidney function. This can sometimes be misleading, so your doctor will review your medical history and other tests to understand the cause.
Do diet or exercise affect creatinine levels?
Yes, diet (especially protein intake) and muscle activity can influence creatinine levels. Eating a high-protein meal or intense exercise shortly before testing may temporarily raise your result. Your doctor may ask you to adjust your diet or timing 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