What is a C-reactive (CRP) protein test?

A c-reactive protein (CRP) test checks the amount of a specific protein in your blood. This protein, CRP, is made by your liver. Normally, you have low levels of CRP, but if there’s inflammation in your body, your liver releases more CRP into your bloodstream. High levels of CRP might indicate a serious health issue causing inflammation.

Inflammation is your body’s way of protecting and healing tissues when they’re injured, infected, or sick. It can be sudden and short-term, which is usually helpful, like when you get a cut and it swells and hurts for a bit. But sometimes, inflammation can stick around too long, harming healthy tissues. This is called chronic inflammation, which can be caused by ongoing infections, autoimmune disorders, or repeated injuries like those from smoking or exposure to certain chemicals.

While a CRP test effectively measures the level of inflammation in your body, it doesn’t identify the specific source or location of the inflammation.

What is it used for?

A CRP test helps identify or keep track of inflammation in both short-term and long-term health issues. This includes:

• Bacteria or viruses cause infections.
• Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis, affect the intestines.
• Autoimmune conditions like lupus, rheumatoid arthritis, and vasculitis.
• Lung conditions like asthma.

Your doctor might use a CRP test to check if treatments for ongoing inflammation are effective. Additionally, if you’re diagnosed with sepsis—a severe response to an infection that reaches your bloodstream, which is life-threatening—a CRP test can help guide treatment decisions.

Why do I need a CRP test?

A CRP test may be necessary if you exhibit symptoms indicative of a bacterial infection, such as:

• Fever or chills
• Fast heartbeat
• Rapid breathing
• Nausea and vomiting

Your healthcare provider might also suggest a CRP test if they suspect you have a long-term condition that causes inflammation. The symptoms for this will vary based on the specific condition.

If you’ve already been diagnosed with an infection or a chronic inflammatory disease, you might need this test to keep an eye on your condition and how well your treatment is working. CRP levels go up and down depending on how much inflammation your body has. If your CRP levels drop, it’s a good sign that your treatment for inflammation is effective, or that you’re getting better on your own.