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C-reactive Protein

(CRP; High-sensitivity C-reactive Protein; hs-CRP)

What Is C-reactive Protein?

C-reactive protein (CRP) is made and put into blood by the liver. CRP levels increase when there is infection or inflammation. They go back to normal after the infection or inflammation clears.

Reason for the Test

A CRP test may be done to help find out if a person has an infection or inflammation. It cannot uncover the type of infection or where the infection is in the body.

The test may also be done to find out if treatment is helpful in people with inflammatory diseases like lupus. Normal CRP levels are a sign that treatment is working.

A CRP test called high-sensitivity C-reactive protein (hs-CRP) may also be used as one test of your heart health. It cannot find out your risk of heart disease, but it may be helpful when done with other blood tests.

Type of Sample Taken

A blood sample will be taken from a vein inside your elbow or the back of your hand.

Prior to Collecting the Sample

You do not need to do anything special before the test.

Tell the doctor about the medicines you take. They may affect test results.

During the Sample Collection

You will be asked to sit. An area inside your elbow will be cleaned with a wipe. A large band will be tied around your arm. The needle will be put in a vein. A tube will collect the blood from the needle. The band on your arm will be taken off. After the blood is collected, the needle will be removed. Gauze will be held on the site to help stop bleeding. You may also be given a bandage. This test takes about 5-10 minutes.

After Collecting the Sample

After the blood sample is taken, you may need to stay seated for 10 to 15 minutes. If you are lightheaded, you may need to stay seated longer. When you feel better, you can leave.

A bit of blood may ooze from the vein beneath the skin. It will cause a bruise. A bruise will usually fade in a day or two.

Call your doctor right away if you have redness, swelling, lasting bleeding, or pain.


A normal CRP level means you do not have an infection or inflammation.

An high CRP level may be a sign of infection or inflammation in the body that may be from things like:

  • Cancer
  • Heart attack
  • Blood infection
  • Connective tissue disease
  • Inflammatory diseases like lupus or rheumatoid arthritis
  • Inflammatory bowel disease
  • Pneumococcal or other pneumonia
  • Rheumatic fever
  • Tuberculosis
  • Other infections

Talk to your doctor about your test results. A test may point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.


C-reactive protein (CRP) and other biomarkers as cardiac risk factors. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T116446/C-reactive-protein-CRP-and-other-biomarkers-as-cardiac-risk-factors. Updated December 3, 2018. Accessed May 15, 2019.

CRP: the test. Lab Tests Online—American Association for Clinical Chemistry website. Available at: http://www.labtestsonline.org/understanding/analytes/crp/test.html. Updated May 3, 2019. Accessed May 15, 2019.

High-sensitivity C-reactive Protein. Lab Tests Online—American Association for Clinical Chemistry website. Available at: https://labtestsonline.org/understanding/analytes/hscrp/. Updated February 6, 2019. Accessed May 15, 2019.

Serum C reactive protein level. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T907196/Serum-C-reactive-protein-level. Updated October 8, 2018. Accessed May 15, 2019.

Last reviewed March 2019 by EBSCO Medical Review Board James P. Cornell, MD  Last Updated: 5/13/2019