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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, a protein produced by your liver in response to inflammation or infection in your body.

Quick summary

["CRP helps doctors track inflammation and identify possible infections or conditions like heart disease."]

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

Key facts at a glance

LOINC
44981-9
Short code
C pneum IgG Ser Ql
Synonyms
C pneum IgG Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is This Test Done?

Your doctor may order this test to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate symptoms such as fever, joint pain, or swelling that might suggest an infection or autoimmune disorder.

What Does a High or Low CRP Level Mean?

Elevated CRP levels often indicate inflammation or infection, but they can also be influenced by other factors like stress, certain medications, or underlying health conditions. Low levels may suggest no active inflammation, but they don’t always mean you’re healthy.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed using nephelometry, a method that measures how particles scatter light to determine protein concentration.

What Are Common Causes of High CRP?

High CRP levels can be caused by infections (like pneumonia or urinary tract infections), inflammatory diseases (such as rheumatoid arthritis or lupus), injuries, or certain medical procedures. It can also be elevated due to stress, smoking, or obesity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum/Plasma)

Frequently asked questions

What does a CRP test tell me about my health?
A CRP test helps your doctor assess whether you have an active inflammatory process or infection, but it’s not a standalone test for diagnosis. It’s often used as part of a broader evaluation to guide treatment decisions.
How often should I get a CRP test?
The frequency depends on your medical condition and your doctor’s recommendations. Some people may need CRP tests regularly to monitor chronic inflammation, while others may only need it if symptoms or other test results suggest inflammation is present.
Can lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet, exercise, smoking, and stress can influence CRP levels. Reducing inflammation through healthy habits may lower CRP, but it’s best to discuss these changes with your healthcare provider.
  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