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Serum Creatinine (Substance Concentration)

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

This test measures the amount of creatinine, a waste product from muscle metabolism, in your blood. It helps assess how well your kidneys are filtering blood.

Quick summary

["Kidney function depends on this test to detect early kidney problems."]

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

Key facts at a glance

LOINC
36064-4
Short code
CT Should-L
Synonyms
CT Should-L
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
100
Critical range
0.1 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
CPT
83721
SNOMED
113079007
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 levels can indicate how efficiently your kidneys are working. High levels may suggest kidney damage or disease, while low levels could signal dehydration or muscle loss.

What to Expect Before the Test

You’ll typically have a small blood sample drawn from your arm. No special preparation is needed unless instructed by your healthcare provider.

Possible Causes of Abnormal Results

Elevated creatinine may result from kidney disease, dehydration, or conditions affecting muscle mass. Low levels might mean dehydration, low protein intake, or severe muscle breakdown.

When to Ask About Results

Discuss any changes in your creatinine levels with your doctor, especially if you have symptoms like swelling, fatigue, or changes in urine output.

Reference range

Optimal: <100 mg/dLN/A

Specimen: serum

Fasting for 12-14 hours preferred. Water is permitted. Avoid alcohol for 24 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine (Serum)

Frequently asked questions

Why might my doctor order this test?
Your doctor may check creatinine levels to monitor kidney health, especially if you have diabetes, high blood pressure, or a history of kidney issues. It can also help assess how well medications are being processed by your kidneys.
What does a high creatinine level mean?
A high creatinine level often signals reduced kidney function, but it can also be influenced by factors like dehydration, recent muscle activity, or certain medications. Your doctor will consider your overall health and other test results to interpret the result.
Can diet affect creatinine levels?
Dietary changes like high-protein intake may temporarily affect creatinine levels, but your doctor will focus on overall kidney function rather than short-term fluctuations from diet alone.
  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