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C-reactive protein (CRP) by nephelometry

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

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

Quick summary

["CRP helps track inflammation, often used to monitor conditions like infections or autoimmune diseases."]

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

Key facts at a glance

LOINC
24774-2
Short code
Deprecated KD-Bl+CS CT
Synonyms
Deprecated KD-Bl+CS CT
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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

What Is CRP Used For?

CRP is primarily used to detect and monitor inflammation in the body. It can help identify infections (such as bacterial infections), assess the activity of autoimmune diseases (like rheumatoid arthritis or lupus), and evaluate the effectiveness of treatments targeting inflammation.

How Is CRP Tested?

The CRP test involves drawing blood from a vein in your arm. The blood sample is then analyzed using nephelometry, a method that measures the amount of CRP in your serum or plasma.

What Does a High CRP Level Mean?

Elevated CRP levels often indicate an ongoing inflammatory process. While high CRP can be caused by infections, injuries, or certain medical conditions, it’s not specific to any single cause. Your healthcare provider will consider your symptoms and other test results to determine the likely cause.

What Does a Low CRP Level Mean?

Low CRP levels usually suggest minimal or no active inflammation. However, very low levels might also be seen in healthy individuals or those with suppressed inflammatory responses, depending on their overall health status.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CRP plays a critical role in diagnosing and managing inflammatory conditions. It’s often used as a screening tool for infections, a marker for disease activity in autoimmune disorders, and a guide for assessing treatment responses. While CRP is not diagnostic on its own, it provides valuable information to help healthcare providers make informed decisions about your care.

Short name

CRP (Nephelometry)

Frequently asked questions

Why might my CRP test be ordered?
Your doctor may order a CRP test to check for signs of inflammation, monitor conditions like infections, autoimmune diseases, or heart disease, or to evaluate how well you’re responding to treatment.
What are common reasons for abnormal CRP levels?
Common reasons for elevated CRP include infections (such as pneumonia or urinary tract infections), autoimmune diseases (like lupus or rheumatoid arthritis), heart disease, certain cancers, or other inflammatory conditions. Low CRP levels may indicate no active inflammation, but they can also occur in healthy individuals or those with suppressed inflammatory responses.
How often should I get a CRP test?
The frequency of CRP testing depends on your medical condition and your doctor’s recommendations. Some people may need CRP tests regularly to monitor chronic inflammatory diseases, while others may only need it occasionally for specific situations, like before or after treatment for an infection or autoimmune condition.
  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