C-Reactive Protein (CRP) Test
Reviewed
Also called: CRP test, c-reactive protein, serum
A c-reactive protein test measures the level of c-reactive protein (CRP) in a sample of your blood. Your liver makes CRP in response to inflammation.
Specimen: Blood
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
Some medicines may affect your results. Don't stop taking any prescription medicines without talking with your provider first.
A health care professional will take a blood sample from a vein in your arm, using a small needle. 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
In general, healthy people have very low amounts of CRP in their blood. A value of 0.8-1.0 milligrams per deciliter (mg/dL) or lower is thought to be a healthy amount.
- CRP 0.8-1.0 mg/dL or lower: A value of 0.8-1.0 milligrams per deciliter (mg/dL) or lower is thought to be a healthy amount. Limitation: A CRP test is sometimes confused with a high-sensitivity-(hs) CRP test. They both measure CRP, but they are used for different conditions. Next step: To make a diagnosis, your provider will look at your CRP results along with the results of other tests, your symptoms, and medical history.
What does high CRP mean?
CRP above normal: Any increases above normal may mean you have inflammation in your body. Limitation: Your CRP test results tell you how much inflammation you have in your body, but not what's causing it or where it is. Next step: To make a diagnosis, your provider will look at your CRP results along with the results of other tests, your symptoms, and medical history.
- 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
To make a diagnosis, your provider will look at your CRP results along with the results of other tests, your symptoms, and medical history.
- 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
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: C-Reactive Protein (CRP) Test