C-reactive protein (CRP) by nephelometry (plasma)

Why Is This Test Done?

Your doctor may order a CRP test to monitor inflammation, detect infections (like pneumonia or sepsis), evaluate conditions such as rheumatoid arthritis or heart disease, or check for signs of tissue damage or autoimmune disorders. It can also help guide treatment decisions for conditions like gout or certain cancers.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves drawing blood from a vein. If you’re taking blood from a fingerstick (e.g., for glucose monitoring), no fasting is required. Always follow your healthcare provider’s instructions.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm to draw blood. You may feel a brief pinch, but it’s usually over quickly. The blood sample is then sent to a lab for analysis using nephelometry, a method that measures how much light a protein scatters to determine its concentration.

What Does the Test Result Mean?

Results are reported in milligrams per deciliter (mg/dL) or micrograms per milliliter (µg/mL). Higher than expected levels may indicate inflammation, infection, or other health issues, while lower levels might suggest reduced inflammation or certain medical conditions. Your doctor will interpret the result in the context of your overall health and symptoms.