Skip to content

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 creatinine test helps check kidney function by evaluating how efficiently your kidneys remove waste from your blood."]

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

Key facts at a glance

LOINC
42368-1
Short code
N men sg W135 Ag Islt Ql Aggl
Synonyms
N men sg W135 Ag Islt Ql Aggl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggl
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 well your kidneys are working. High levels may suggest kidney problems, while low levels might raise concerns about muscle metabolism or hydration status.

What to Expect Before the Test

You may be asked to fast for a few hours before the test, but this depends on your doctor’s instructions. Bring any medications you’re currently taking, as some may affect results.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. The process is quick and usually causes minimal discomfort. You may feel a slight pinch, but it won’t take long.

What the Results Mean

Results are compared to a standard range to determine if your kidneys are functioning normally. Your doctor will discuss any deviations with you during your follow-up.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Chronic kidney disease (CKD) is often detected early through creatinine testing. Elevated levels may signal impaired kidney function, requiring further evaluation or lifestyle adjustments. Low levels could indicate dehydration, muscle disorders, or errors in testing.

Short name

Creatinine Level

Frequently asked questions

How often should I get this test?
Your doctor will determine the frequency based on your health history, symptoms, and kidney function. Regular monitoring may be recommended if you have conditions like diabetes or hypertension.
Can diet or medications affect creatinine levels?
Yes, certain foods (like red meat) and medications (e.g., NSAIDs) can influence results. Always inform your doctor about all medications and supplements you take.
What if my results are outside the normal range?
If your creatinine level is higher than expected, your doctor may order additional tests to check kidney function further. If it’s lower, they may review your hydration status or muscle health.
  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