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Serum or Plasma Creatinine Concentration (Qualitative/Quantitative)

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

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

Quick summary

["Kidney function check via creatinine levels."]

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

Key facts at a glance

LOINC
73951-6
Short code
RCS-4 Bld Ql
Synonyms
RCS-4 Bld Ql
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to monitor kidney health, especially if you have symptoms like swelling, fatigue, or changes in urine output. It’s also used before surgeries, during pregnancy, or if you have conditions like diabetes or high blood pressure that can affect kidney function.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a larger panel. Drink plenty of water the day before to help dilute your blood for accurate results.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm. The sample is sent to a lab for analysis, where creatinine levels are measured using an automated method (often enzymatic or spectrophotometric).

What the Results Mean

Higher-than-normal levels may indicate reduced kidney function, while lower levels could suggest dehydration or muscle breakdown. Your doctor will interpret results in relation to your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level (Serum/Plasma)

Frequently asked questions

Why did my doctor order this test?
Your doctor may have recommended it to check for kidney problems, monitor a chronic condition, or prepare for a procedure. Common reasons include symptoms like swelling, changes in urine, or if you have a history of kidney disease.
What does a ‘normal’ result mean?
A ‘normal’ result doesn’t mean your kidneys are perfectly healthy—it just means your creatinine level falls within the expected range for your age, sex, and body size. Your doctor will discuss what your specific result means for you.
Can diet affect my creatinine test results?
Yes! Eating a high-protein diet or drinking too much water can temporarily change your creatinine level. Your doctor may ask you to follow a standard diet or avoid extreme fluid intake before the test for more accurate results.
  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