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Serum or Plasma Creatinine Concentration (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 or plasma. It helps assess how well your kidneys are filtering blood.

Quick summary

["A key test for kidney function and overall health."]

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

Key facts at a glance

LOINC
40556-3
Short code
ER Ag Tiss Ql ImStn
Synonyms
ER Ag Tiss Ql ImStn
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
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 Matters

Creatinine levels can indicate how efficiently your kidneys are working. High levels may suggest kidney problems, while low levels could indicate dehydration or muscle breakdown.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before testing if your doctor specifies it. Wear comfortable clothing and plan to stay for about 15 minutes.

During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. If you’re nervous, let your doctor know—they can help with comfort measures.

Possible Results and Next Steps

Your results will be compared to standard ranges, though individual values can vary based on age, sex, and health. If your levels are outside the expected range, your doctor may recommend further testing or adjustments to your care plan.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Creatinine is a reliable marker for kidney function because it’s produced consistently by muscle metabolism and easily filtered by the kidneys. Elevated levels often signal kidney damage, while persistently low levels may warrant investigation into conditions like dehydration or muscle disorders.

Short name

Creatinine

Frequently asked questions

What causes creatinine levels to be high?
High creatinine levels can result from kidney disease, dehydration, severe muscle damage, or conditions that reduce blood flow to the kidneys. Your doctor may also consider medications or underlying health issues when interpreting results.
How often should I get this test?
The frequency depends on your health status. People with kidney concerns or chronic conditions may need this test more often, while healthy individuals may only require it during routine checkups or if symptoms arise.
Can diet affect creatinine levels?
Dietary protein intake can influence creatinine levels, but the effect is usually small. High-protein diets may temporarily raise levels, while dehydration can also impact results. Always follow your doctor’s guidance on timing and preparation.
  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