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Serum or Plasma Creatinine Concentration (Mass Concentration)

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

This test measures how much creatinine is in your blood or plasma. Creatinine is a waste product from muscle metabolism that your kidneys filter out. It helps assess how well your kidneys are working.

Quick summary

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

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

Key facts at a glance

LOINC
56733-9
Short code
ENA PCNA Ab Ser Ql IB
Synonyms
ENA PCNA Ab Ser Ql IB
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ib
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

Your kidneys normally filter waste products like creatinine from your blood. High levels of creatinine can indicate poor kidney function, while low levels might suggest overhydration or other conditions. This test is often used alongside other kidney function tests to diagnose or monitor kidney disease.

What to Expect Before the Test

You may be asked to fast for 4–12 hours before the test, depending on your doctor’s instructions. Avoid strenuous activity or consuming certain medications that could affect results. Bring a list of all medications you’re taking to your appointment.

What Happens During the Test

A healthcare provider will draw blood from a vein in your arm. The process is quick and usually painless. You may feel a slight pinch, but it won’t take long. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to a general reference range, but your actual values may vary based on factors like age, sex, muscle mass, and hydration status. High creatinine levels may signal kidney problems, while very low levels may need further investigation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

How often should I get this test?
Your doctor will determine how often you need this test based on your health history, symptoms, and kidney function. For example, people with diabetes or high blood pressure may need it more frequently than others.
Can diet affect my creatinine levels?
Yes, diet can influence creatinine levels. High-protein foods or dehydration can raise them, while adequate hydration may lower them. Always follow your doctor’s advice on diet and fluid intake before testing.
What if my results are outside the normal range?
If your results are abnormal, your doctor will discuss them with you and may recommend further tests or adjustments to your treatment plan, such as monitoring kidney function more closely or modifying medications.
  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