C-reactive protein (CRP) concentration in serum/plasma

A C-reactive protein (CRP) test measures the amount of CRP, a protein made by your liver, in your blood. Your body produces more CRP when there is inflammation somewhere in your body, so this test helps your doctor look for infection, check for inflammatory conditions such as rheumatoid arthritis or lupus, or see how well a treatment is working over time.

Your healthcare provider may order this test to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate responses to treatments. It can also help diagnose infections or assess risks for conditions like heart disease.

No special preparation is usually needed, and you can generally eat and drink as you normally would unless your doctor gives you different instructions. Before the test, tell your care team about any medicines, vitamins, or supplements you take, and mention any recent illness, injury, surgery, or vaccination, because these can temporarily raise your CRP level.

No special preparation is usually needed. You may fast before the test if instructed, but your provider will confirm. Bring any medications or supplements you’re taking, as they can sometimes affect results.

During the test, a nurse or phlebotomist will wrap an elastic band around your upper arm and draw a small sample of blood from a vein, usually on the inside of your elbow or the back of your hand. You may feel a quick sting when the needle goes in, but the blood draw takes only a few minutes, and a small bandage is placed over the spot afterward.

A small needle will be used to draw blood from a vein in your arm. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The process takes only a few minutes.

Results are usually described as normal (low) or high. A normal result suggests there is no significant inflammation in your body. A high result means inflammation is present, but the test does not show where it is or what is causing it. Your doctor may repeat the test, order additional blood work or imaging, or refer you to a specialist to identify the source. Always review your results with your doctor to understand what they mean for your health.

Results are typically reported in milligrams per liter (mg/L). High levels may indicate inflammation, infection, or other health issues, while low levels may suggest no active inflammation. Your provider will discuss results with you and recommend next steps based on your overall health.