C-reactive protein (serum/plasma) concentration, measured by nephelometry

Why CRP is Tested

Doctors may order a CRP test to monitor conditions like infections (e.g., pneumonia, urinary tract infections), inflammatory diseases (e.g., rheumatoid arthritis, lupus), or to check for signs of tissue damage or healing after surgery or injury. It can also help evaluate responses to treatments.

How the Test Works

Your blood sample is sent to a lab where it is analyzed using nephelometry, a method that detects the amount of CRP in your serum or plasma. The test measures the protein’s concentration, which is then compared to a reference range to determine your results.

What to Expect Before the Test

You can typically have this test done at a doctor’s office, clinic, or lab. No special preparation is usually needed, but you may be asked to fast for 8–12 hours if your doctor specifies it for other tests. Avoid strenuous activity or recent infections before the test if instructed.

What the Results Mean

Results are reported in milligrams per deciliter (mg/dL) or micrograms per milliliter (µg/mL). Higher CRP levels often indicate inflammation, while lower levels suggest minimal or no inflammation. Your doctor will interpret results based on your medical history and symptoms.