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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 or urine. It helps assess kidney function.

Quick summary

["Kidney health and filtering efficiency are evaluated with this simple blood or urine test."]

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

Key facts at a glance

LOINC
103244-0
Short code
XR Great toe-L GE 2V
Synonyms
XR Great toe-L GE 2V
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
20
Ref high
400
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
CPT
82670
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 filtered by your kidneys. High levels may indicate reduced kidney function, while low levels could suggest overhydration or muscle loss. This test is often used alongside other kidney function tests to diagnose or monitor conditions like chronic kidney disease.

Blood vs. Urine Testing

Your doctor may order a blood test to measure creatinine levels directly. Alternatively, a 24-hour urine test collects all creatinine excreted over a day to calculate creatinine clearance, which reflects kidney function more precisely.

Common Uses

Doctors use creatinine tests to check for kidney problems, monitor kidney disease progression, evaluate kidney function before surgeries or procedures, and assess hydration status. It’s also part of routine health check-ups for older adults or those with risk factors like diabetes or high blood pressure.

What to Expect

A blood test involves a simple needle prick at a vein (usually in your arm). For a 24-hour urine test, you’ll collect all urine for a full day, typically in a container. Follow your doctor’s instructions carefully to ensure accurate results.

Reference range

Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Creatinine

Frequently asked questions

What does a high creatinine level mean?
High creatinine levels in blood may signal impaired kidney function, where waste products aren’t filtered properly. In urine, elevated levels could indicate kidney damage or obstruction. However, other factors like muscle mass or dehydration can also affect results, so results should be interpreted with other tests and clinical context.
What does a low creatinine level mean?
Low creatinine levels in blood might suggest dehydration, overhydration, or low muscle mass. In urine, low levels could mean kidneys aren’t filtering enough creatinine or that you’re retaining fluids. Always discuss results with your healthcare provider.
How often should I get this test?
Your doctor will determine the frequency based on your health status. For example, people with kidney disease may need tests more often, while healthy individuals might only need baseline checks. Regular follow-ups are important if you have risk factors like diabetes or high blood pressure.
  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