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Serum or Plasma Creatinine Concentration (Mass Concentration)

Published: August 9, 2026Updated: August 17, 2026

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

Quick summary

["A creatinine test helps evaluate kidney function and detect early kidney problems."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
7589-5
Short code
BPHISTR
Synonyms
Black Pepper BasoBnd Ab Qn
Category
chemistry
Sample
whole-blood
Container
Heparinized whole blood tube (green top, sodium or lithium heparin); EDTA tubes acceptable for some methodologies
Units
N/A
Ref low
25
Ref high
200
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 2 years
Method
Flow cytometry; cell-based histamine release assay
CPT
86003
SNOMED
39579001
Specimen volume
5-10 mL whole blood (minimum 3 mL for pediatric samples)
Stability
Refrigerated (2-8°C): up to 24 hours; ambient temperature (18-25°C): process within 8 hours of collection; do not freeze
Hemolysis max
100
Lipemia max
300
Icterus max
25
TAT
24–72 hours
Order
routine

Why This Test Matters for Kidney Health

Creatinine is a byproduct of muscle breakdown that your kidneys filter from your blood. High levels can indicate poor kidney function, while low levels might suggest overhydration or other conditions. This test is often used alongside other measures, like blood urea nitrogen (BUN), to assess kidney health.

How the Test Works

Your blood or plasma sample is analyzed using a method that detects the amount of creatinine present. Common techniques include enzymatic assays or high-performance liquid chromatography (HPLC). The test measures the concentration of creatinine in milligrams per deciliter (mg/dL) or other standardized units.

When You Might Need This Test

Doctors may order a creatinine test if you have symptoms like swelling, fatigue, or frequent urination; if you have a history of kidney disease; or if you’re taking medications that can affect kidney function. It’s also part of routine check-ups for people at higher risk of kidney problems, such as those with diabetes or high blood pressure.

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 metabolic panel. Drink plenty of water the day before to ensure your kidneys are functioning normally. Avoid taking certain supplements or medications that could interfere with results, such as certain pain relievers or vitamins.

Reference range

NCBI: CK 25-200 U/LN/A

Specimen: whole-blood

No fasting required. Patient should avoid antihistamines, corticosteroids, and other immunomodulatory medications for 5-7 days prior to testing as directed by the ordering physician. Leukotriene receptor antagonists should be discontinued 24 hours prior.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Creatinine

Frequently asked questions

How creatinine levels can signal kidney issues or other health conditions.
High creatinine levels may signal reduced kidney function, meaning your kidneys aren’t filtering blood as well as they should. This can happen due to kidney disease, dehydration, or conditions like heart failure or severe muscle disorders. Low levels might indicate overhydration, liver disease, or certain medications. Regular monitoring of creatinine levels helps track kidney health over time and adjust treatments accordingly.
What does a creatinine test tell me about my health?
A creatinine test primarily assesses kidney function by measuring how well your kidneys filter waste products. It doesn’t diagnose specific conditions alone but can help identify kidney problems early. Your doctor will use the results along with other tests and symptoms to determine if further action is needed.
Can diet or hydration affect my creatinine levels?
Yes, diet and hydration can influence creatinine levels. Drinking too little water can raise creatinine because your blood becomes more concentrated. Eating a high-protein diet may temporarily increase creatinine levels, though this usually normalizes after a few days. Always follow your doctor’s advice on preparation 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 17, 2026. · Read our editorial policy