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C-reactive protein (CRP) by nephelometry (serum/plasma)

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, infection, or other health conditions."]

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

Key facts at a glance

LOINC
24789-0
Short code
XR tomo Kdny-Bl
Synonyms
XR tomo Kdny-Bl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr-tomography
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 CRP testing to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate infections such as pneumonia or sepsis. It can also help guide treatment decisions, especially in cases where symptoms are unclear.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before the draw if your lab requires it, but this depends on the specific test protocol. Bring any medications you’re currently taking to your appointment.

During the Test

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but the procedure usually takes just a few minutes. You can rest comfortably afterward.

What the Results Mean

Results are interpreted based on your overall health, symptoms, and medical history. Elevated CRP levels may indicate inflammation, infection, or autoimmune conditions, while lower levels may suggest no active inflammation. Your doctor will discuss the results in the context of your care plan.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What Are Common Causes of Elevated CRP?
Elevated CRP can be caused by infections (like bacterial pneumonia or urinary tract infections), inflammatory diseases (such as rheumatoid arthritis or lupus), injuries, or other conditions like heart disease or certain cancers. It may also rise temporarily after surgery or trauma.
What Are Common Causes of Low CRP?
Low CRP levels are more common and often indicate no significant inflammation. However, very low levels might raise concerns if you have known inflammatory conditions, as they could suggest treatment effectiveness or a lack of underlying disease activity.
How Often Should I Get This Test?
The frequency depends on your medical needs. Your doctor may order CRP testing periodically if you have chronic conditions like arthritis or heart disease, or if you’re being monitored for infection or inflammation. Follow your provider’s recommendations.
  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