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Serum or Plasma Creatinine Concentration (Mass Concentration)

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

This test measures the level 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 creatinine test helps check kidney function and detect early kidney problems."]

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

Key facts at a glance

LOINC
39075-7
Short code
XR Toes AP+Obl
Synonyms
XR Toes AP+Obl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
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 This Test Matters

Creatinine is a byproduct of muscle breakdown and is normally filtered out by your kidneys. High levels can indicate poor kidney function, while low levels may suggest dehydration or overhydration. This test is often used alongside other kidney function tests to monitor conditions like chronic kidney disease or acute kidney injury.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw (serum/plasma) or, in some cases, a urine sample (though creatinine in urine is less commonly measured alone). Avoid excessive exercise or heavy meals 24 hours before if instructed by your provider.

What the Results Mean

Results are typically compared to reference ranges based on age, sex, and overall health. Elevated levels may signal kidney issues, while persistently low levels could warrant further investigation into hydration status or muscle mass.

Common Conditions Monitored

This test is frequently used to monitor kidney disease, evaluate kidney function before surgeries or procedures, and assess response to treatments for conditions like diabetes or hypertension.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine

Frequently asked questions

How often do I need this test?
The frequency depends on your health. Healthy adults may not need it routinely unless advised by a doctor. People with kidney disease, diabetes, or high blood pressure may have it checked more often, such as every 3–6 months.
Can diet affect creatinine levels?
Dietary protein intake can influence creatinine levels, but the effect is usually small. Avoiding excessive protein for a few days before testing may help standardize results, but this is not always necessary.
What if my results are abnormal?
If your creatinine level is high, your doctor may recommend further tests (like blood urea nitrogen or urine tests) or adjustments to your treatment plan. If low, they may check for dehydration or other causes.
  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