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Tests & Procedures

C-Reactive Protein (Blood)Proteína C reactiva (en suero)

C-Reactive Protein (Blood)

Does this test have other names?


What is this test?

The C-reactive protein (CRP) test is used to detect inflammation in your body. It does this by measuring the amount of CRP in your blood. CRP is a protein made by the liver and released into the bloodstream. Blood levels may be higher when you have inflammation or an infection. Because CRP levels often go up before symptoms of pain or fever appear and drop down as you recover, the CRP test is especially useful for tracking infections.

Because C-reactive protein is part of the immune system, your levels of it rise whenever you have inflammation in your body. In fact, inflammation can trigger a thousand-fold jump in CRP. Still, the test doesn't pinpoint where the inflammation is coming from or what is causing it.

A high-sensitivity CRP test (hs-CRP) may be used to measure your heart disease risk even if you seem healthy. It can detect much smaller differences in CRP levels than the regular CRP test. 

Why do I need this test?

You may need this test if your doctor suspects you have an infection such as osteomyelitis, which involves bone, or sepsis, a potentially life-threatening condition commonly known as blood poisoning.

Symptoms of sepsis may include fever and chills, headache, pain, nausea, vomiting, disorientation, rash, and shortness of breath. The level of CRP in your blood shoots up within a few hours of a serious infection.  

Your doctor may also order the test if he or she suspects you have an inflammatory condition or an autoimmune disease, such as rheumatoid arthritis. CRP levels are elevated in people with these conditions. This test may also be used to monitor flare-ups and recovery.  Symptoms of rheumatoid arthritis include joint swelling and pain, morning stiffness, tiredness, weight loss, and low-grade fevers.

If you are being treated for a chronic inflammatory condition or an infection, this test may be used to see if the treatment is working.


What other tests might I have along with this test?

Because the CRP test tells you only if you have inflammation and doesn't pinpoint what is causing it, your doctor will likely order more tests. These may include:

  • Erythrocyte sedimentation rate, or ESR, test. Like the CRP, this test measures inflammation. It's not as sensitive as the CRP, but it's easy to do and provides complementary information, so many doctors will order it at the same time.




What do my test results mean?



How is this test done? 


Does this test pose any risks?


What might affect my test results?

A number of factors, such as obesity, lack of exercise, cigarette smoking, and diabetes, may cause your CRP levels to be slightly higher than normal.

How do I get ready for this test?

No special preparation is needed for this test, but be sure your doctor knows about all medicines, herbs, and supplements you are taking. This includes medicines that don't need a prescription. 

If you take certain medicines, such as nonsteroidal anti-inflammatory drugs (Aleve or Advil), aspirin, or steroids, you levels may be lower than normal.