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C-reactive protein (CRP) by nephelometry in serum

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

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

Quick summary

["CRP helps track inflammation, often used to check for infections or other health issues causing swelling."]

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

Key facts at a glance

LOINC
44980-1
Short code
C pneum Ab sp1 Ser Ql
Synonyms
C pneum Ab sp1 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 This Test Matters

CRP is a marker that helps doctors assess whether your body is fighting inflammation. High levels may signal infections, autoimmune conditions, or other health problems that need monitoring or treatment.

Common Uses

Doctors may order this test to monitor chronic conditions like rheumatoid arthritis, to check for infections (e.g., pneumonia, sepsis), or to evaluate response to treatments targeting inflammation.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample drawn from your arm. If you’re on blood thinners, let your doctor know before the test.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL). While reference ranges vary by lab, very high levels may indicate severe inflammation or infection, while very low levels might suggest reduced immune response.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP (Serum)

Frequently asked questions

What causes elevated CRP levels?
Elevated CRP levels can be caused by infections (like bacterial infections), inflammatory diseases (such as arthritis), injuries, or other conditions like heart disease or certain cancers. Chronic stress or smoking may also contribute.
What if my CRP is high?
If your CRP is high, your doctor may recommend further testing (like blood cultures or imaging) to identify the cause. Treatment may include antibiotics, anti-inflammatory medications, or lifestyle changes depending on the underlying issue.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on activity, diet, and underlying health conditions. Regular monitoring helps track how well treatments are working or if inflammation is worsening.
  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