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Serum Creatinine (Creatinine, Blood)

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

This test measures the level of creatinine, a waste product from muscle metabolism that your kidneys filter from your blood. High levels may indicate kidney function issues.

Quick summary

["Kidney health depends on this test—check levels if you suspect kidney problems."]

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

Key facts at a glance

LOINC
103301-8
Short code
XR Abd GE 2V
Synonyms
XR Abd 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

What Does This Test Measure?

Creatinine is a byproduct of muscle breakdown, which your kidneys normally remove from your blood. This test helps assess how well your kidneys are filtering waste. While creatinine levels alone don’t diagnose kidney disease, they’re often checked alongside other tests like blood urea nitrogen (BUN) to evaluate kidney function.

Why Might Your Doctor Order This Test?

Your doctor may order a serum creatinine test if you have symptoms like fatigue, swelling, frequent urination, or if you have risk factors for kidney problems, such as high blood pressure, diabetes, or a family history of kidney disease. It’s also part of routine check-ups for certain conditions.

How Is the Test Done?

A small blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed to measure creatinine levels. The test usually takes a few minutes, and you may feel slight discomfort from the needle insertion.

What Are Common Results?

Results are typically reported in milligrams per deciliter (mg/dL) or micromoles per liter (µmol/L). While exact reference ranges vary by lab, higher than expected levels may signal reduced kidney function.

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

Serum Creatinine

Frequently asked questions

Why is creatinine important in kidney health?
Creatinine is a key marker for kidney function because it reflects how well your kidneys filter waste. Elevated levels can indicate impaired kidney function, though they don’t always mean kidney disease is present. Your doctor may use creatinine alongside other tests to assess kidney health, especially if you have symptoms or risk factors.
How do creatinine levels change with age?
Creatinine levels can naturally rise with age due to reduced muscle mass. However, if your levels increase significantly beyond what’s expected for your age, it may signal kidney issues that need further evaluation.
Can diet affect creatinine levels?
Dietary protein intake can influence creatinine levels, but the effect is usually small. High-protein diets may temporarily raise creatinine, while very low-protein diets might lower it. Your doctor will consider overall health, not just diet, when interpreting results.
  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