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Plasma or Serum Creatinine (with or without adjustment for dialysis)

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

This test measures the amount 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

Kidney function and dialysis effectiveness depend on this test.

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

Key facts at a glance

LOINC
64366-8
Short code
INCENTERPATIENTSDIALYZINGNOCTURNALLYANDMORETHAN4TIMESPERWEEKATENDOF
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 This Test Is Done

Your doctor may order this test if you have kidney disease, are undergoing dialysis, or if they suspect your kidneys aren’t working as well as they should. It’s also checked regularly in patients on dialysis to monitor progress and adjust treatment.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into a vein (usually in your arm) to draw blood. If you’re on dialysis, your creatinine levels may be interpreted differently due to dialysis’s impact on waste removal.

What the Results Mean

Creatinine levels can vary based on muscle mass, hydration status, and dialysis frequency. Higher levels may indicate reduced kidney function, while lower levels might suggest overhydration or less muscle mass. Your doctor will interpret results in the context of your overall health.

How Dialysis Affects Creatinine

If you’re dialyzing nocturnally (at night) more than 4 times a week, your creatinine levels may be lower than expected because dialysis removes waste products more aggressively during sleep. Your doctor may use a special formula to adjust results for this.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Creatinine Level

Frequently asked questions

Your doctor may use this test to track kidney function, adjust dialysis settings, or detect early kidney damage. In patients on dialysis, abnormal levels can signal issues like over-dialysis (hypotension) or inadequate clearance.
This test helps ensure your kidneys are working within safe limits or that your dialysis is effectively removing waste.
How often will I need this test?
The frequency depends on your kidney health and dialysis schedule. Your doctor will tell you how often to get tested, but it’s often done monthly or as needed to monitor changes.
What if my creatinine level is higher than expected?
Higher levels may mean your kidneys aren’t filtering blood well, or your dialysis may need adjustment. Your doctor will discuss this with you and may recommend further tests or changes to your treatment plan.
  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