C-Reactive Protein (CRP) Test

Why this test may be ordered

• To check for a bacterial infection if you have symptoms like fever, chills, rapid heart rate, rapid breathing, nausea, and vomiting.
• To monitor for infection after surgery.
• To monitor your condition and treatment if you have an infection or a chronic condition that causes inflammation.
• To help make treatment decisions if you have sepsis.

Preparation and collection

Tell your provider about any supplements or medicines you take, including magnesium and NSAIDs like ibuprofen and aspirin. Do not stop taking any prescription medicines without talking to your provider first.

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This process usually takes less than five minutes.

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

Your CRP test results show the amount of inflammation in your body. In general, healthy people have very low CRP levels. A value of 0.8-1.0 mg/dL or lower is considered healthy. Higher levels indicate inflammation, but the test does not identify the cause or location.

• CRP level 1.0 mg/dL or lower (within normal range): You have a low amount of inflammation, which is typical for a healthy person. Limitation: Some people with chronic inflammation may still have normal CRP levels. Next step: Your provider will interpret this result along with your symptoms and other tests.
• CRP level higher than 1.0 mg/dL: You have inflammation in your body. This could be due to an infection, autoimmune disorder, chronic disease, or other causes. Limitation: This test does not identify the cause or location of inflammation. Factors like insomnia, depression, hormone therapy, obesity, and sex (females may have slightly higher levels) can affect results. Next step: Your provider will likely order additional tests and review your symptoms and medical history to determine the cause.

• The test measures inflammation but does not identify its cause or location.
• Certain medicines, supplements, and lifestyle factors can affect CRP levels.
• Normal CRP levels do not rule out all inflammatory conditions.

What to do next

Your provider will interpret your CRP results along with other tests, your symptoms, and medical history to determine the cause of inflammation and guide treatment.

• What does my CRP level mean?
• What could be causing inflammation in my body?
• Do I need any other tests?
• How will my CRP level affect my treatment?
• Should I be concerned about sepsis?

Evidence source

U.S. National Library of Medicine: C-Reactive Protein (CRP) Test