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

Why CRP Matters in Your Health

CRP is a marker that signals your body’s immune response. High levels may indicate inflammation, which can be caused by infections, injuries, or certain medical conditions like rheumatoid arthritis or heart disease. Your doctor may use this test to track how your body is responding to treatment or to check for early signs of problems.

When You Might Need This Test

You may have this test if you have symptoms of inflammation, such as fever, joint pain, or swelling. It’s also used to monitor chronic conditions like heart disease, kidney disease, or certain autoimmune disorders. Sometimes, doctors check CRP levels after surgery or during treatment for infections to see how your body is healing.

What to Expect Before the Test

No special preparation is usually needed for this test. You may have a small needle inserted into a vein in your arm to draw blood. If you’re taking blood from your home, follow your healthcare provider’s instructions carefully. Avoid strenuous activity or eating/drinking for a short time before testing if your provider recommends it.

What the Results Mean

CRP results are often reported in milligrams per liter (mg/L). A low level (near zero) usually means little to no inflammation. Higher levels may suggest an active inflammatory process, but results alone don’t diagnose a specific condition. Your doctor will interpret the results in the context of your symptoms and medical history.