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C-reactive protein (CRP) concentration, serum/plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of C-reactive protein in your blood, a substance produced by your liver in response to inflammation.

Quick summary

["CRP helps identify 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
35958-8
Short code
CT IAC
Synonyms
CT IAC
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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 inflammation in your body. It can help diagnose conditions like infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis), or to monitor healing after surgery or injury. CRP levels can also be used to assess risk for heart disease or other chronic conditions.

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 your blood is drawn early in the morning. Avoid strenuous activity or taking certain medications (like NSAIDs) that could affect inflammation levels. Your blood will be drawn from a vein, typically in your arm.

What to Expect During the Test

The test involves a small needle inserted into your arm to draw blood. It usually takes a few minutes, and you may feel a brief pinch. Afterward, a bandage will be applied to the site. The blood sample is then sent to a lab for analysis.

What the Results Mean

CRP levels vary depending on your health. Higher-than-normal levels may indicate inflammation, while lower levels suggest little to no inflammation. Your doctor will interpret the results in the context of your medical history and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP Level

Frequently asked questions

What does a high CRP level mean?
A high CRP level often signals inflammation in your body, which can be caused by infections, injuries, autoimmune diseases, or other conditions. For example, it may help doctors confirm a diagnosis of an infection or monitor how well a treatment is working. However, CRP alone isn’t diagnostic—it’s usually one piece of a larger picture.
What does a low CRP level mean?
A low CRP level typically means there’s little to no inflammation detected in your blood. This could be normal if you’re healthy, but it may also suggest that an underlying inflammatory condition is under control or absent. Always discuss results with your healthcare provider.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, recent illnesses, medications, or lifestyle factors like stress or diet. If you have a chronic condition (e.g., arthritis), your CRP levels may be checked regularly to track changes in 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