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STDWatch
Dr. Patricia Shelton

Dec 02, 20227 min read

C-Reactive Protein Test

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When you’re getting blood tests, there are often multiple different things that are tested, and these aren’t always explained to you ahead of time. When you see the results of your blood test, CRP, meaning C-reactive protein, might be one of the things that’s listed. Many people aren’t quite sure what this means, or why this test might be done. 

How can you interpret your CRP report? What does it mean if you have high CRP levels?

What is a C-reactive protein test?

C-reactive protein is made in the liver. The levels of this protein in the blood rise in response to any type of inflammation in the body. When the immune system is activated, then C-reactive protein levels will go up.

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There are generally two main reasons that a doctor might order a CRP test. One is in the process of diagnosis. If C-reactive protein is high, causes like chronic inflammatory diseases or infections are more likely. If it’s normal, then something else is a more likely diagnosis.

Another reason for testing CRP is to measure a patient’s risk of a heart attack. It’s been well established that people with higher CRP levels are more likely to experience a heart attack in the next 10 years than those with normal levels. If you have risk factors for heart disease, your doctor may measure CRP to help determine your risk level for having a heart attack. If you’ve already had one heart attack, your doctor may measure CRP to help determine how likely you are to have another one. Usually, a type of CRP test known as high-sensitivity CRP, or hs-CRP, is used for this purpose.

Patients sometimes refer to this as the “C protein test” or measuring their “C protein levels,” but it’s actually technically known as “C-reactive protein” or CRP, rather than just C protein.

What is the C-reactive protein normal range?

When you’re looking at your blood results, CRP or hs-CRP should be specified. The results will be interpreted slightly differently, depending on the type of test and the reason for the test.

For the standard C-reactive protein test, levels should be at 10 mg/L or below. There’s no such thing as a CRP level that’s too low. (However, there are certain types of diseases, such as liver disease, that can stop the body’s production of CRP. In these patients, CRP may not rise even when they have an infection or inflammation in the body.) 

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For the high sensitivity C-reactive protein test, levels higher than 2 mg/L are considered to put you at higher risk for heart disease, while lower levels are associated with a lower risk.

What does it mean if your C-reactive protein is high?

If you get abnormal C-reactive protein test results, meaning that your level is above the cutoff for what’s considered to be normal, then there are a few different possibilities for what this might indicate.

With C-reactive protein, high levels indicate that there’s inflammation in your body. One use of CRP is to determine whether a patient’s symptoms are caused by an inflammatory or infectious disease. For example, CRP is commonly measured in arthritis testing. When trying to determine the cause of your joint inflammation, a doctor may order this test. If your C-reactive protein is high, meaning that there’s a higher level of inflammation in your body, this points to an autoimmune diagnosis like rheumatoid arthritis or lupus, rather than a wear-and-tear condition or injury.

If you’ve had the CRP or hs-CRP test because you may be at risk of heart attacks, your doctor will use your specific value to help determine your risk of having a heart attack in the next 10 years. If you have high C-reactive protein test results, meaning that your level is above what’s considered to be normal, this is only one factor that’s used in determining your risk of a future heart attack. By itself, a high CRP level doesn’t always mean that you’re at a high risk.

Can you test C-reactive protein on your own?

More and more people are becoming aware of the damaging effects of chronic inflammation on a person’s health. It’s believed that chronic inflammation raises the risk of a number of serious diseases, including cancer. Because of this, many people want to test their CRP levels, so they can find out whether they have chronic inflammation.

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You can order a CRP test yourself. There are services available that will either allow you to order the test on your own and then go to a laboratory for your blood draw, or that send you a home test kit and ask you to take your blood sample yourself through a fingerprick. You’ll then get your results online in a few days. If your CRP levels are normal, this gives you peace of mind that you’re unlikely to have hidden chronic inflammation. If they’re high, then you’ll want to talk with a doctor to figure out what’s causing the high level and what to do about it.

Sources

C-reactive protein. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/c-reactive-protein-test/about/pac-20385228. Accessed 15 Sep 2022.

C-Reactive Protein (CRP) Test. Medline. https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/. Accessed 15 Sep 2022.

C Reactive Protein. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK441843/. Accessed 15 Sep 2022.

Singh N, Baby D, et al. Inflammation and Cancer. Ann Afr Med. 2019 Jul-Sep; 18(3): 121–126. doi: 10.4103/aam.aam_56_18


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