C-reactive protein (CRP) – Serum/plasma concentration

Your doctor may order a CRP test to check for inflammation in your body. It is often used to help diagnose an infection, monitor a chronic inflammatory condition such as rheumatoid arthritis or lupus, or assess your risk of heart disease. The test can also show whether treatment for an infection or inflammatory disease is working.

Your doctor may order a CRP test if you have symptoms of inflammation, such as fever, pain, or swelling, or if you’re at higher risk for conditions like heart disease or autoimmune disorders. It can also be used to check for infections, such as pneumonia or urinary tract infections, or to monitor treatment progress for conditions like arthritis or lupus.

The CRP test is a simple blood draw. A healthcare professional will clean the skin on your arm, wrap a band around your upper arm, and insert a small needle into a vein to collect a sample. The process usually takes less than five minutes, and you may feel only a quick pinch. You can return to your normal activities right away, and no fasting or special preparation is needed for a standard CRP test.

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch when the needle is inserted, but the procedure is quick. The sample is sent to a lab for testing. Results are typically available within a few days.

Most healthy adults have CRP levels below 10 milligrams per liter (mg/L), although exact reference ranges vary between laboratories. A higher level means inflammation is present somewhere in your body, commonly due to infection or an inflammatory condition. Because the test cannot show where the inflammation is or what is causing it, your doctor will review your CRP result together with your symptoms, medical history, and other test results before making a diagnosis. Always discuss your results with your healthcare provider rather than drawing conclusions on your own.

CRP levels can vary depending on your health status. Higher levels often indicate inflammation, but a single test result alone isn’t enough to diagnose a condition. Your doctor will consider your overall health, symptoms, and other test results when interpreting your CRP level.

The CRP test is widely used to detect and monitor infections, track inflammatory conditions such as rheumatoid arthritis, lupus, and inflammatory bowel disease, and identify flare-ups of these illnesses. A related version, the high-sensitivity CRP (hs-CRP) test, helps estimate the risk of heart attack and stroke. Doctors also rely on CRP measurements to see how well antibiotics, anti-inflammatory medicines, or other treatments are working.

CRP is commonly used to screen for cardiovascular risks, track inflammation in chronic conditions, and guide treatment decisions for infections or autoimmune diseases. It’s also sometimes used as a general health check or in research studies.