Skip to content

Serum or Plasma Creatinine Concentration (Substance Concentration)

Published: August 9, 2026Updated: August 16, 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 check kidney function by measuring how well your kidneys remove waste from your blood."]

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

Key facts at a glance

LOINC
71848-6
Short code
SaO2 DF BldCoA
Synonyms
SaO2 DF BldCoA
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Matters

Creatinine is a byproduct of muscle breakdown and is normally filtered out by your kidneys. High levels may indicate kidney problems, while low levels could suggest muscle disorders or overhydration. This test is often used alongside other measures, like blood urea nitrogen (BUN), to evaluate kidney health.

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 larger panel. Drink plenty of water the day before to ensure accurate results. Avoid heavy exercise or strenuous activity that day.

What Happens During the Test

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The sample is sent to a lab for analysis. If you’re tested for urine creatinine, you’ll collect a sample in a sterile container.

What the Results Mean

Results are compared to a general reference range, but individual ranges can vary by lab. High creatinine levels may signal kidney dysfunction, while very low levels could warrant further investigation for conditions like muscle atrophy or dehydration.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Creatinine levels are a key indicator of kidney function. Chronic kidney disease (CKD) often presents with elevated creatinine, as the kidneys struggle to filter waste effectively. Doctors may use this test to monitor kidney health in people with diabetes, hypertension, or other chronic conditions. It’s also useful in diagnosing acute kidney injury or assessing pre-existing kidney disease progression.

Short name

Creatinine

Frequently asked questions

What causes creatinine levels to change?
Several factors can affect creatinine levels, including muscle mass (higher muscle = higher creatinine), dehydration or overhydration, certain medications (like NSAIDs or contrast dyes), or conditions like muscle injuries or infections. If you’ve had recent surgery, trauma, or changes in diet (e.g., high-protein meals), these could influence your results.
How often should I get this test?
The frequency depends on your health status. People with kidney disease or risk factors (like diabetes or high blood pressure) may need this test every few months or annually. Your doctor will determine the best schedule based on your medical history and symptoms.
Can diet affect creatinine levels?
Yes, diet can impact creatinine levels. High-protein foods (like red meat or supplements) may temporarily raise creatinine, while low-protein diets could lower it. Hydration status also matters—drinking enough water helps maintain normal levels. Always discuss dietary changes with your healthcare provider before making major adjustments.
  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