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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 check for inflammation or infection.

Quick summary

["CRP helps track inflammation, guiding treatment decisions for conditions like infections, autoimmune diseases, or post-surgery monitoring."]

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

Key facts at a glance

LOINC
18492-9
Short code
C trach G+F+K IgM Titr Ser IF
Synonyms
C trach G+F+K IgM Titr Ser IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82784
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 CRP Matters in Your Health

CRP is produced by your liver in response to inflammation. Elevated levels may signal conditions such as infections (e.g., pneumonia, urinary tract infections), autoimmune disorders (e.g., rheumatoid arthritis), or other inflammatory processes. It’s also used to assess risk for heart disease and monitor treatment effectiveness in some cases.

When This Test Is Ordered

Your healthcare provider may order this test if you have symptoms of infection (e.g., fever, fatigue), suspected autoimmune disease, or if you’re undergoing treatment for inflammation-related conditions. It can also be used to monitor chronic conditions like heart disease or after surgery.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s part of a fasting panel. Bring any medications you’re currently taking to your appointment.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. The sample is then analyzed in a lab using nephelometry, a method that measures how particles scatter light to detect CRP levels.

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 (above normal reference ranges) often indicates inflammation or infection. However, levels can also be elevated due to stress, certain medications, or other health conditions. Your provider will interpret results in the context of your symptoms and medical history.
What does a low CRP level mean?
A low CRP level generally suggests minimal inflammation. However, very low levels might raise concerns if you’re experiencing symptoms of infection or inflammation, so results should always be reviewed by your healthcare provider.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, treatments, or other factors. Regular monitoring may be needed if you have a chronic condition or ongoing treatment for inflammation.
  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