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C-reactive protein (CRP) concentration in plasma by nephelometry

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 your body. CRP helps your immune system fight infections and injuries.

Quick summary

["CRP helps doctors assess inflammation, often used to monitor conditions like infections, autoimmune diseases, or after surgery."]

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

Key facts at a glance

LOINC
90357-5
Short code
C trach+GC pnl Nph NAA+probe
Synonyms
C trach+GC pnl Nph NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
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 Might You Need This Test?

Your doctor may order this test to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, or evaluate responses to treatments. It can also help identify infections or determine if you’re healing properly after surgery or illness.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast before the test if it’s done in a different context (like lipid panels), but for CRP alone, eating or drinking normally is fine. Bring any medications or questions to your appointment.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The blood sample is sent to a lab where it’s analyzed using a nephelometry method to measure CRP levels.

What Are Results Typically Used For?

Results help track inflammation trends over time. High levels may indicate active infection, inflammation, or autoimmune activity, while low levels suggest minimal inflammation. Your doctor will interpret results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Plasma)

Frequently asked questions

What Does a High CRP Level Mean?
A high CRP level often signals inflammation, which can be caused by infections (like pneumonia or urinary tract infections), autoimmune diseases (like lupus or rheumatoid arthritis), or other conditions causing tissue damage. It’s not specific to one disease but is a general marker of your body’s response to stress.
What Does a Low CRP Level Mean?
Low CRP levels usually mean your body is not experiencing significant inflammation. However, very low levels might raise questions about underlying conditions that suppress inflammation, so results should always be reviewed by a healthcare provider.
How Often Should I Get This Test?
The frequency depends on your health condition. Doctors may recommend regular CRP checks for people with chronic inflammatory diseases, those recovering from surgery, or those at higher risk for infections. Follow your doctor’s advice for timing and follow-ups.
  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