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Serum or Plasma Creatinine Concentration (Mass 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

["A creatinine test helps check kidney function by measuring waste in your blood."]

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

Key facts at a glance

LOINC
79936-1
Short code
RV FAC A4C
Synonyms
RV FAC A4C
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-d-a-c-measured-by-planimetry
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. If your kidneys aren’t working well, creatinine levels in your blood can rise. This test is often used alongside other kidney function tests to detect early kidney damage or disease.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into a vein (usually in your arm) to draw blood. If you’re tested for plasma, your blood will be collected into a special tube that separates blood cells from plasma. Avoid strenuous activity or heavy meals 12 hours before the test if instructed by your provider.

What the Results Mean

Higher than expected creatinine levels may indicate reduced kidney function, while lower levels might suggest dehydration or overhydration. Your doctor will interpret results in relation to your overall health and other tests.

Common Causes of Abnormal Results

Elevated creatinine can result from kidney disease, dehydration, severe muscle injury, or conditions that reduce blood flow to the kidneys. Low levels may occur with overhydration, certain medications, or liver disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine

Frequently asked questions

How often should I get this test?
Your doctor will determine how often you need this test based on your health, symptoms, and risk factors. For example, people with diabetes or high blood pressure may need it more frequently to monitor kidney health.
Can diet or exercise affect creatinine levels?
Dietary changes (like eating more protein) or intense exercise can temporarily raise creatinine levels. However, your doctor will consider these factors when interpreting results, so follow their advice on lifestyle adjustments.
What if my results are out of the normal range?
If your results are abnormal, your doctor may recommend further tests, like additional bloodwork or imaging, to investigate the cause. They’ll also discuss lifestyle changes or treatments to support kidney health 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