C-Reactive Protein (Blood)

Does this test have other names?


What is this test?

The C-reactive protein (CRP) test is used to find inflammation in your body. Inflammation could be caused by different types of conditions, such as an infection or autoimmune disorders like rheumatoid arthritis or inflammatory bowel disease. This test measures the amount of CRP in your blood. CRP is a protein made by the liver and sent into the bloodstream. Blood levels may be higher when you have inflammation or an infection. Because CRP levels often go up before you have symptoms of pain or fever and drop down as you recover, the CRP test is especially useful for tracking infections. 

Because CRP is part of the immune system, your levels of it rise whenever you have inflammation in your body. But the test doesn't show where the inflammation is or what is causing it.


Why do I need this test?

You may need this test if your healthcare provider thinks you have an infection. For example, it may be osteomyelitis, which involves bone. Or it may be a potentially life-threatening condition called sepsis or blood poisoning.





What other tests might I have along with this test?


  • Erythrocyte sedimentation rate (ESR) test. Like the CRP, this test measures inflammation. It's not as sensitive as the CRP. But it's easy to do and gives more information. So many healthcare providers will order it at the same time.

  • Antinuclear antibody (ANA) test. The ANA test measures autoantibodies that attack your cells. This is important in diagnosing some autoimmune diseases.  

  • Rheumatoid factor (RF). This test is done to help diagnose and monitor rheumatoid arthritis.

  • Anticyclic citrullinated peptide (anti-CCP) antibodies. This test is done to help diagnose and monitor rheumatoid arthritis. 

What do my test results mean?



How is this test done? 


Does this test pose any risks?


What might affect my test results?


Certain medicines can cause your CRP levels to be lower than normal. These include nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, and steroids.

How do I get ready for this test?


Online Medical Reviewer: Chad Haldeman-Englert MD
Online Medical Reviewer: Kenny Turley PA-C
Online Medical Reviewer: Maryann Foley RN BSN
Date Last Reviewed: 8/1/2020