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Plasma or 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 kidney function.

Quick summary

["Kidney health is checked with this simple blood test."]

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

Key facts at a glance

LOINC
9909-3
Short code
P wave dur L-V3
Synonyms
P wave dur L-V3
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 monitor kidney function, detect early kidney damage, or evaluate symptoms like fatigue, swelling, or changes in urine output. It’s also used before certain procedures or medications that can affect the kidneys.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re currently taking.

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 using a specialized method.

What the Results Mean

Higher than expected levels may indicate reduced kidney function, while lower levels could suggest muscle breakdown or other conditions. Your doctor will interpret results in relation to your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine Level

Frequently asked questions

What causes creatinine levels to be high?
High creatinine levels can result from kidney disease, dehydration, severe muscle damage, or certain medications. Chronic kidney disease is the most common cause, but other factors like heart failure or diabetes may also play a role.
What should I do if my creatinine level is abnormal?
If your results are outside the expected range, your doctor will discuss next steps, which may include further testing, lifestyle changes (like hydration or diet adjustments), or monitoring for kidney-related conditions. Follow their guidance closely.
Does diet affect creatinine levels?
Dietary protein intake can influence creatinine levels, but the test itself doesn’t measure protein directly. Staying hydrated and avoiding excessive protein may help if your doctor recommends it, but always follow their advice.
  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