Test Overview

A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood. C-reactive protein measures general levels of inflammation in your body.

High levels of CRP are caused by infections and many long-term diseases. But a CRP test cannot show where the inflammation is located or what is causing it. Other tests are needed to find the cause and location of the inflammation.

Why It Is Done

This test is used to:

• Check for infection after surgery.
• Identify and keep track of infections and diseases that cause inflammation, such as:
  • Lymphoma (cancer of the lymph nodes).
  • Giant cell arteritis (painful swelling of the blood vessels in the head and neck).
  • Rheumatoid arthritis (painful swelling of the tissues that line the joint).
  • Osteomyelitis (infection of a bone).

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How long the test takes

The test will take a few minutes.

Watch

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Results are usually available within 24 hours.

High levels of CRP are caused by infections and many long-term diseases.