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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 or infection.

Quick summary

["CRP helps track 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
35397-9
Short code
EBV DNA Mar Ql NAA+probe
Synonyms
EBV DNA Mar Ql 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 This Test Is Done

Doctors may order CRP testing to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, evaluate infections, or assess recovery after surgery or injury. It can also help guide treatment decisions for conditions like heart disease.

How the Test Works

A small blood sample is drawn, typically from your arm. The lab uses nephelometry—a precise method—to measure the amount of CRP in your blood. CRP levels rise quickly in response to inflammation, making this test useful for early detection.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to avoid certain medications or foods that could affect results (e.g., aspirin or supplements). If you have a history of bleeding disorders, let your doctor know before the test.

What the Results Mean

Results are reported in milligrams per liter (mg/L). Higher than normal levels may indicate inflammation, infection, or an underlying condition requiring further evaluation. Your doctor will interpret results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP (Nephelometry)

Frequently asked questions

What causes elevated CRP levels?
Elevated CRP can be caused by infections (like pneumonia or urinary tract infections), autoimmune diseases (such as rheumatoid arthritis), trauma, surgery, or other inflammatory conditions. It’s not specific to one condition, so doctors often use it alongside other tests for diagnosis.
What does a normal CRP level indicate?
A normal CRP level suggests minimal inflammation, but it doesn’t rule out all causes of inflammation. Your doctor may still recommend follow-up tests if symptoms persist or if you have an ongoing condition requiring monitoring.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on activity, diet, stress, or underlying health changes. Regular monitoring may be needed for chronic conditions, and your doctor will adjust treatment plans if levels change significantly.
  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