Serum or Plasma Substance Concentration (Mass) – C-Reactive Protein (CRP)

Why CRP Matters in Your Health

CRP is a marker for inflammation, which is the body’s natural response to injury, infection, or illness. High CRP levels may signal an active inflammatory process, such as infections, autoimmune diseases (e.g., rheumatoid arthritis), or conditions like heart disease. Doctors use CRP to monitor how well treatments are working or to check for recurring issues.

When This Test Is Ordered

Your doctor may order a CRP test to evaluate symptoms like fever, joint pain, or swelling, or to monitor chronic conditions. It’s also used before surgeries, during pregnancy, or to assess risk for heart disease. Some tests are done as part of routine check-ups or to guide decisions about medications.

What to Expect Before the Test

No special preparation is needed for this test. You may have blood drawn from a vein in your arm, or a sample of plasma/serum may be collected if you’re already undergoing a blood draw for another test. If you’re taking blood thinners, let your doctor know before the test.

What the Results Mean

Results are reported in milligrams per liter (mg/L). A low CRP level (typically below 1 mg/L) suggests little to no inflammation. Higher levels may indicate an active inflammatory process, but results alone don’t diagnose a specific condition. Your doctor will interpret results in the context of your symptoms and medical history.