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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

["Kidney function check: creatinine levels help detect early kidney problems."]

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

Key facts at a glance

LOINC
86621-0
Short code
MRB mecC Islt/Spm Ql
Synonyms
MRB mecC Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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 work hard to filter waste and extra fluid from your blood. Creatinine is a natural byproduct of muscle activity and is efficiently removed by healthy kidneys. If your kidneys aren’t working well, creatinine levels can build up in your blood, which may indicate kidney disease or damage.

What Causes Creatinine Levels to Change?

Several factors can affect creatinine levels, including muscle mass (more muscle means higher levels), dehydration, diet (especially protein intake), and certain medications. Kidney disease, heart conditions, or severe infections can also influence these levels.

When Might This Test Be Ordered?

Your doctor may order a creatinine test to monitor kidney function before or after treatments like chemotherapy, to check for kidney problems after surgery, or if you have symptoms like swelling, fatigue, or changes in urine output.

What to Expect During the Test

This test is usually done by drawing blood from a vein in your arm. No special preparation is needed, but you may be asked to stop certain medications temporarily if instructed by your healthcare provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

How is creatinine used in diagnosis?
Creatinine levels are often used alongside other tests, like blood urea nitrogen (BUN), to assess kidney function. Elevated levels may signal kidney problems, while very low levels could indicate muscle wasting or liver disease.
What does a high creatinine level mean?
A high creatinine level may suggest your kidneys aren’t working as well as they should, which can lead to buildup of waste products in your blood. This could be due to kidney disease, dehydration, or other health conditions.
Can diet affect creatinine levels?
Yes, your diet—especially protein intake—can influence creatinine levels. Eating more protein may temporarily raise your level, but your body usually balances it out. Always follow your doctor’s advice about diet and test 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