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Creatinine in Serum or Plasma (Mass Concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of creatinine, a waste product from muscle metabolism, in your blood. It helps assess kidney function.

Quick summary

["A key test for kidney health and filtering ability."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
50756-6
Short code
CK Bld-mCnc
Synonyms
CK Bld-mCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
22
Ref high
198
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82553
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 check how well your kidneys are working, especially if you have symptoms like swelling, fatigue, or changes in urine output. It’s also used to monitor kidney disease, diabetes, or heart conditions that can affect kidney function over time.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re currently taking.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a small pinch, but it usually takes only a few minutes. The blood sample is sent to a lab for analysis.

What Are the Results Mean?

Higher-than-normal levels may suggest kidney problems, while lower levels could indicate muscle breakdown or other conditions. Your doctor will interpret results in the context of your overall health.

Reference range

Adult males: 22-198 U/L; Females: 22-198 U/LN/A

Specimen: whole-blood

No special preparation required. Inform provider of any chest pain or symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum/Creatinine

Frequently asked questions

How often should I expect this test?
The frequency depends on your health status. If you have kidney disease, diabetes, or another condition affecting kidneys, your doctor may order this test more often—every few months or annually. Otherwise, it may be done as needed for routine check-ups or symptoms.
What can affect my creatinine levels?
Several factors can influence creatinine levels, including muscle mass (more muscle = higher levels), dehydration, or certain medications. Severe illness, bleeding, or muscle damage can temporarily spike levels. Always discuss any changes in activity, diet, or medications with your doctor before testing.
Do I need to avoid certain foods or drinks before this test?
No specific diet restrictions apply, but if your test is part of a metabolic panel, you may be asked to fast. Avoid excessive alcohol or high-protein foods 24 hours before testing, as they can affect results. Follow your doctor’s instructions for the most 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 17, 2026. · Read our editorial policy