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Serum Creatinine (with optional 24-hour urine collection for creatinine clearance calculation)

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

This test measures the level of creatinine, a waste product from muscle metabolism, in your blood. 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
31911-1
Short code
N men Ag CSF-aCnc
Synonyms
N men Ag CSF-aCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What Does This Test Measure?

Creatinine is a byproduct of muscle breakdown and is naturally filtered out of your blood by your kidneys. High levels can indicate poor kidney function, while low levels may suggest dehydration or muscle loss. This test is often used alone or in combination with other tests to evaluate kidney health.

Why Is This Test Done?

Your doctor may order this test to monitor kidney function, especially if you have symptoms like swelling, fatigue, or changes in urine output. It’s also used before certain surgeries, during pregnancy, or if you have conditions like diabetes or high blood pressure that put you at risk for kidney problems.

What to Expect Before the Test

No special preparation is needed for a simple serum creatinine test. If your doctor requests a 24-hour urine sample for creatinine clearance, collect all urine over 24 hours in a container provided by your lab. Drink enough water to maintain normal urine output but avoid excessive fluid intake.

What Happens During the Test?

A small blood sample is drawn from a vein in your arm, usually in a doctor’s office or lab. The process is quick and may cause a slight pinch. If you have a 24-hour urine test, you’ll need to return the container to the lab on time.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Creatinine

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab. Follow-up with your healthcare provider if you have questions about your results.
Can I eat or drink before this test?
For a standard serum creatinine test, no special diet or fasting is required. For a 24-hour urine test, avoid excessive alcohol or certain medications (like NSAIDs) that may affect urine output or kidney function.
What if my creatinine level is abnormal?
If your results are outside the expected range, your doctor may recommend further testing, like additional blood tests (e.g., blood urea nitrogen) or imaging to investigate the cause. They’ll discuss next steps with you based on your overall health.
  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