C-Reactive Protein (CRP) Test

A c-reactive protein test measures the level of c-reactive protein (CRP) in a sample of your blood. Your liver makes CRP in response to inflammation. Inflammation is your body's way of protecting your tissues and helping them heal from an injury, infection, or other disease.

When it's acute (sudden) and for a short time, inflammation is helpful. For example, when you get a cut on your skin, the area around the cut may turn red and swell. These are signs that inflammation is working to stop infection.

Inflammation acts in a similar way when responding to germs or harmful substances (toxins) inside your body. If inflammation lasts too long, however, it can damage healthy tissues. This is called chronic (long-term) inflammation, and it is most often caused by certain autoimmune disorders.

Chronic inflammation can also happen if your tissues are repeatedly injured or irritated, for example from smoking or chemicals in the environment.

Why this test is done

You may need this test if you have symptoms of a bacterial infection, such as:

• Fever or chills
• Rapid heart rate
• Rapid breathing
• Nausea and vomiting

You may also need a CRP test if your provider wants to:

• Check for a chronic condition that causes inflammation.
• Monitor for infection after surgery.
• Monitor your condition and treatment if you have an infection or a chronic condition.
• Make treatment decisions if you have sepsis. Sepsis is your body's extreme response to an infection that spreads to your blood. It's a life-threatening medical emergency.

CRP levels rise and fall depending on how much inflammation is in your body. So, if your CRP levels fall, it's a sign that your treatment for inflammation is working or that you're healing on your own.

How to prepare

Some medicines may affect your results. So, tell your provider about any supplements or medicines that you take, including magnesium and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen and aspirin. Don't stop taking any prescription medicines without talking with your provider first.

Sample type

Blood

Other names for this test

c-reactive protein, serum