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C-Reactive Protein (CRP) by Immunoassay (Serum/Plasma)

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 in the body.

Quick summary

["CRP helps identify and monitor inflammation, often used to check for infections, autoimmune conditions, or other inflammatory diseases."]

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

Key facts at a glance

LOINC
65781-7
Short code
London Plane (nPla a) 2 IgE Qn
Synonyms
London Plane (nPla a) 2 IgE Qn
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

What Is C-Reactive Protein?

C-reactive protein (CRP) is a marker produced by your liver when your body is fighting inflammation. It rises in response to infections, injuries, or conditions like arthritis, heart disease, or autoimmune disorders. Your doctor may order this test to assess whether inflammation is present or to monitor treatment progress.

Why Might You Need This Test?

Doctors often use CRP to diagnose or track conditions like infections (e.g., pneumonia, urinary tract infections), inflammatory diseases (e.g., rheumatoid arthritis, lupus), or to evaluate heart disease risk. It may also help guide decisions about medications or treatments.

How Is the Test Done?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed using an immunoassay method to measure CRP levels. Results are typically available within 24–48 hours.

What Do My Results Mean?

Results are reported in milligrams per liter (mg/L) or micrograms per milliliter (µg/mL). Higher than normal levels may signal inflammation, but interpretation depends on your overall health and symptoms. Your doctor will discuss findings with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CRP in Healthcare

Short name

CRP

Frequently asked questions

What causes CRP levels to change?
CRP levels can rise due to infections (like flu or UTIs), injuries, surgeries, or certain medications. Chronic conditions such as rheumatoid arthritis or heart disease may also lead to consistently elevated levels. Low or normal CRP can indicate no active inflammation, but it doesn’t rule out all causes.
How often should I get this test?
Your doctor will determine how often to check CRP based on your health needs. Some people get it yearly for heart health monitoring, while others may need it more frequently if they have ongoing conditions like arthritis or heart disease.
Can CRP levels be affected by diet or lifestyle?
Yes, diet and lifestyle can influence CRP levels. Eating a heart-healthy diet, staying physically active, and managing stress may help lower inflammation. Avoiding smoking and limiting alcohol can also support lower CRP levels.
  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