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C-reactive protein (CRP) by nephelometry (plasma)

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

This test measures the level of C-reactive protein in your blood, a protein produced by the liver in response to inflammation.

Quick summary

["CRP helps identify inflammation, which can signal infections, injuries, or other health issues."]

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

Key facts at a glance

LOINC
26665-0
Short code
C trach F Ab Ser Ql
Synonyms
C trach F Ab Ser Ql
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 Is This Test Done?

Your doctor may order this test to check for signs of inflammation in your body. It can help diagnose conditions like infections, autoimmune diseases, or after an injury or surgery. CRP levels can also be monitored over time to see how your body is responding to treatment for conditions like arthritis or heart disease.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into a vein in your arm to draw blood. It usually takes a few minutes, and you might feel a brief pinch or discomfort. If you’re on blood thinners, let your doctor know before the test.

What the Results Mean

CRP levels can vary depending on your health and medical history. Higher levels often indicate inflammation, while lower levels suggest minimal or no inflammation. Your doctor will interpret the results in the context of your overall health and symptoms.

Common Conditions Monitored

This test is often used to monitor conditions like infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis, lupus), heart disease, or after surgery to track healing progress.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP Plasma

Frequently asked questions

What Does a High CRP Level Indicate?
A high CRP level may signal inflammation caused by infections, injuries, or autoimmune diseases. It can also be elevated after surgery or during certain chronic conditions like heart disease or certain cancers. Your doctor will use these results alongside other tests and symptoms to guide diagnosis and treatment.
What Does a Low CRP Level Indicate?
A low CRP level usually means there is little to no inflammation in your body. However, it doesn’t rule out all causes of illness—other tests may be needed to confirm the diagnosis. If your CRP level is consistently low but you have symptoms, discuss this with your doctor.
How Often Should CRP Be Checked?
The frequency of CRP testing depends on your health condition and treatment plan. For example, people with chronic diseases like rheumatoid arthritis may have CRP checked regularly to monitor disease activity. Your doctor will determine how often you need this test based on your specific needs.
  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