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Serum Creatinine (Creatinine Level)

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

["Kidney function and waste removal depend on this test."]

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

Key facts at a glance

LOINC
36063-6
Short code
CT Shoulder-Bl
Synonyms
CT Shoulder-Bl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.4
Ref high
4
Critical range
0.1 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
CPT
84443
SNOMED
301343003
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 Is This Test Done?

Your doctor may order this test to check for kidney problems, monitor kidney disease, or evaluate overall kidney function. It’s often used alongside other tests like blood urea nitrogen (BUN) to assess kidney health, especially if you have symptoms like swelling, fatigue, or changes in urine output.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader kidney function panel. Drink plenty of water the day before to help your kidneys work normally. If you’re on certain medications (like NSAIDs or diuretics), let your doctor know—these can affect results.

How the Test Works

A small blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab, where it’s analyzed to measure creatinine levels. The test is quick and typically done in a doctor’s office or lab.

What the Results Mean

Higher than expected creatinine levels may suggest kidney problems, while lower levels could indicate dehydration or muscle loss. Your doctor will compare your results to your baseline and other tests to determine if further action is needed.

Reference range

Adult: 0.4-4.0 mIU/LN/A

Specimen: serum

Take your thyroid medication after the blood draw if applicable. No fasting required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine

Frequently asked questions

What causes creatinine levels to change?
Creatinine levels can rise due to kidney disease, dehydration, muscle breakdown, or certain medications. They may also drop if you’re dehydrated or have very little muscle mass. Factors like age, sex, and body size can also influence results.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition. For healthy individuals, it’s often checked only if symptoms or risk factors (like high blood pressure or diabetes) suggest kidney issues. Regular monitoring may be needed if you have chronic kidney disease.
Can diet affect creatinine levels?
Diet alone doesn’t change creatinine levels, but what you eat can affect kidney function indirectly. High-protein diets may temporarily increase muscle breakdown, which could slightly impact results. Staying hydrated is more important for kidney health than diet for this test.
  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