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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 the liver in response to inflammation.

Quick summary

["CRP helps doctors identify and monitor inflammation in the body."]

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

Key facts at a glance

LOINC
18566-0
Short code
J Pnt ST Amp+60ms L-V5
Synonyms
J Pnt ST Amp+60ms L-V5
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 healthcare provider may order this test to check for signs of inflammation, assess conditions like infections, autoimmune diseases, or heart disease, or monitor treatment progress for conditions such as arthritis or other inflammatory disorders.

What Does a High or Low CRP Level Mean?

A higher than normal CRP level often suggests inflammation is present. While it doesn’t pinpoint the cause, it can guide decisions about further testing or treatments. A very low CRP level may indicate no active inflammation, but it’s not definitive on its own.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum or plasma, which is then analyzed in a lab using nephelometry, a method that measures how particles scatter light to detect protein levels.

Common Conditions Monitored

CRP is commonly used to monitor conditions like rheumatoid arthritis, lupus, heart attacks, infections (such as pneumonia or sepsis), and other inflammatory diseases. It can also help track how well you’re responding to treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Nephelometry)

Frequently asked questions

CRP is a sensitive marker for inflammation but isn’t specific to any single condition. It’s often used alongside other tests to provide a clearer picture of your health status, especially in diagnosing or managing chronic inflammatory diseases.
Your CRP level can help your healthcare provider determine if you need additional tests or treatments. For example, a consistently high CRP might prompt further investigation into possible infections or autoimmune activity.
What factors could affect my CRP levels?
Several factors can influence CRP levels, including recent infections, injuries, surgeries, or certain medications. Stress, smoking, and even some foods can also temporarily raise CRP. It’s important to discuss any recent changes in your health or lifestyle with your provider.
How soon will I get my results?
Results are typically available within a few days to a week, depending on your lab’s processing times. Your healthcare provider will discuss the results with you and explain what they mean for your 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