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C-reactive protein (CRP) serum concentration

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

This test measures the level of C-reactive protein in your blood, a marker often used to assess inflammation or infection.

Quick summary

["CRP helps doctors track inflammation, which can signal infections, autoimmune conditions, or other health issues."]

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

Key facts at a glance

LOINC
47052-6
Short code
C pneum Ab Ser IF-aCnc
Synonyms
C pneum Ab Ser IF-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 CRP Tested?

Your doctor may order this test to check for signs of inflammation, monitor chronic conditions like arthritis, or evaluate symptoms such as fever, fatigue, or joint pain that could indicate an infection or other health problem.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab to measure CRP levels using an immunoassay method.

What Does CRP Mean?

Elevated CRP levels often point to inflammation, which can be caused by infections, injuries, autoimmune diseases, or other conditions. However, CRP alone isn’t diagnostic—it’s usually one piece of a larger picture.

Common Reasons for Testing

Doctors may use CRP to monitor treatment progress for conditions like rheumatoid arthritis, lupus, or other inflammatory diseases. It’s also useful in evaluating fever of unknown origin or assessing risk for heart disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP is a non-specific marker, meaning it can rise in many situations, including infections, trauma, or even stress. High levels may prompt further testing to identify the underlying cause, while low levels don’t always mean no inflammation is present.

Short name

CRP

Frequently asked questions

What Are Normal CRP Levels?
There’s no single ‘normal’ range since it varies by lab and individual health. Low levels (often <1 mg/L) suggest minimal inflammation, while higher levels may signal more significant activity.
Can CRP Levels Change Over Time?
Yes, CRP levels can fluctuate based on recent infections, illnesses, or even minor activities like exercise. Your doctor may retest CRP after a few weeks to see if levels improve with treatment.
Does Diet or Exercise Affect CRP Levels?
Moderate exercise and a balanced diet can sometimes lower CRP, but results vary. Avoiding extreme stress or infections may also help keep levels more stable.
  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