Serum or plasma concentration of C-reactive protein (CRP) measured by nephelometry

Why Is This Test Done?

Your healthcare provider may order this test to check for signs of inflammation, monitor conditions like rheumatoid arthritis, heart disease, or infections, or evaluate responses to treatments. CRP levels can also help assess risk for certain conditions, such as heart attacks or strokes.

A high CRP level often indicates inflammation, infection, or an autoimmune condition. A low level suggests minimal inflammation, but it doesn’t rule out other causes. Your results will be interpreted by your healthcare provider based on your overall health and symptoms.

A blood sample is taken from a vein, usually in your arm. The blood is processed to separate serum or plasma, which is then analyzed using nephelometry—a method that measures how much light is scattered by the protein in the sample. This test doesn’t require fasting.

CRP is commonly used to monitor conditions like infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., lupus, rheumatoid arthritis), and inflammatory diseases (e.g., inflammatory bowel disease). It can also help track how well you’re responding to treatments.

Elevated CRP levels may indicate increased risk for heart disease or cardiovascular events. While CRP alone doesn’t diagnose heart disease, it can be part of a broader assessment to guide preventive care or treatment decisions.

No special preparation is needed for this test. You can eat and drink as usual. After the blood draw, you may experience mild bruising or soreness at the site, but this usually goes away quickly.

Results are typically reported in milligrams per liter (mg/L). Your healthcare provider will compare your results to your baseline or to your symptoms and medical history to determine what they mean for you.