Skip to content

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 damage."]

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

Key facts at a glance

LOINC
9925-9
Short code
Q wave Dpth L-AVF
Synonyms
Q wave Dpth L-AVF
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
CPT
85610
SNOMED
396252006
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 out of your blood by your kidneys. High levels can indicate poor kidney function, while low levels may suggest overhydration or other conditions. This test is often used alongside other measures to evaluate kidney health.

What to Expect Before the Test

No special preparation is needed for a simple blood creatinine test. For a 24-hour urine creatinine test, you’ll collect all urine over a full day and return it to the lab. Follow your healthcare provider’s instructions carefully.

Common Causes of Abnormal Results

Elevated creatinine levels may signal kidney disease, dehydration, or conditions affecting muscle mass. Low levels might suggest dehydration, overhydration, or certain medications. Always discuss results with your doctor.

When This Test Is Ordered

Your doctor may order a creatinine test to monitor kidney function, diagnose kidney disease, check for dehydration, or evaluate conditions like heart failure, diabetes, or high blood pressure.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

How is creatinine clearance calculated if urine is collected?
Creatinine clearance is calculated using your blood creatinine level and the amount of creatinine excreted in your urine over 24 hours. This ratio helps determine how efficiently your kidneys filter waste. If urine is not collected, creatinine levels alone are used to assess kidney function.
What does a creatinine test tell me about my kidneys?
A creatinine test provides a snapshot of your kidney function by measuring how well your kidneys remove waste. While it doesn’t directly show kidney damage, high levels may indicate reduced filtering ability, prompting further evaluation. Your doctor will interpret results in the context of your overall health.
Can diet affect creatinine levels?
Dietary protein intake can influence creatinine levels, as muscle breakdown produces this waste. However, short-term changes in diet are unlikely to cause significant fluctuations. Long-term high-protein diets may require monitoring, especially if you have kidney concerns.
  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