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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 in your blood, a marker often used to check for inflammation or infection.

Quick summary

["CRP helps doctors assess inflammation, guide treatment, and monitor conditions like infections or autoimmune diseases."]

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

Key facts at a glance

LOINC
43845-7
Short code
C pneum Ab Titr Ser IF
Synonyms
C pneum Ab 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
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 healthcare provider may order a CRP test to evaluate symptoms such as fever, joint pain, or swelling. It can also help monitor conditions like heart disease, arthritis, or infections like pneumonia or sepsis. Sometimes, it’s used to check for hidden inflammation in people without obvious symptoms.

What Does a High or Low CRP Level Mean?

A higher than normal CRP level often signals inflammation or infection. A low level may mean your body isn’t inflamed, but it doesn’t rule out other conditions. Your results will be interpreted by your doctor based on your overall health and medical history.

How Is the CRP Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab, where it’s analyzed using a nephelometry method to measure CRP levels accurately.

What Are Common Causes of Elevated CRP?

Elevated CRP can be caused by infections (like colds or urinary tract infections), injuries, surgeries, or certain medical conditions such as rheumatoid arthritis or heart disease. Stress, smoking, or certain medications can also affect CRP levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What does a CRP test measure exactly?
A CRP test measures the concentration of C-reactive protein, a protein produced by your liver in response to inflammation or infection. It’s not specific to any single disease but is a general marker of the body’s inflammatory response.
How soon after a possible infection or injury will CRP levels rise?
CRP levels can begin to rise within hours of an infection or injury and may peak within a few days. They often return to normal within a week or two, depending on the cause. Your doctor will interpret the timing based on your symptoms and medical history.
Can CRP levels be affected by diet or lifestyle?
Yes, factors like diet, exercise, smoking, and stress can influence CRP levels. For example, a healthy diet and regular physical activity may help lower CRP. Smoking and obesity are known to increase CRP, so maintaining a balanced lifestyle can support better test results.
  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