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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 marker often used to assess inflammation or infection.

Quick summary

["CRP helps doctors check for inflammation, infection, or other health conditions."]

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

Key facts at a glance

LOINC
109481-2
Short code
ECV9 Ab Msmt CSF
Synonyms
ECV9 Ab Msmt CSF
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to monitor conditions like arthritis, infections (such as pneumonia or urinary tract infections), or to check for signs of inflammation after surgery or injury. It can also be used to screen for certain heart risks or to evaluate how well treatments are working.

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 is less common for CRP. Bring your lab results or questions to your appointment.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood is then sent to the lab for analysis using nephelometry, a method that measures how much light is scattered by particles in the sample.

What Are Possible Results?

Results are reported in milligrams per deciliter (mg/dL). Higher than normal levels may indicate inflammation, infection, or other health issues. Your results will be interpreted by your healthcare provider based on your medical history and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Nephelometry)

Frequently asked questions

What does a high CRP level mean?
A high CRP level suggests there may be inflammation or infection in your body. This could be due to an infection (like a cold or flu), an autoimmune condition (like lupus or rheumatoid arthritis), or other health issues. Your doctor will review your results along with other tests and symptoms to determine the cause.
What does a low CRP level mean?
A low CRP level usually means there is little to no inflammation in your body. However, it doesn’t rule out all possible causes of inflammation or infection. If you have symptoms like fever, pain, or fatigue, further testing may be needed to identify the underlying issue.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, recent infections, medications, or other factors. If your CRP level is monitored regularly (e.g., for chronic conditions), your doctor may adjust treatments or interventions based on these changes.
  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