C-Reactive Protein (CRP): What Levels Mean

Dr. Clarisse Bezerra
Medical review: Dr. Clarisse Bezerra Family Doctor CRM 16976-CE / OMP 69634
Created by: Tua Saude editing team
Key points
  • C-reactive protein (CRP) is a liver-made protein that usually rises when there is inflammation or infection in the body.
  • Normal CRP levels are generally below 10 mg/L, while higher levels may suggest inflammation, bacterial infection, severe infection, or sepsis.
  • A high-sensitivity CRP test can help estimate heart disease risk, but CRP results should always be interpreted with other test results.

C-reactive protein (CRP) is a protein made by the liver that usually rises when there is inflammation or infection in the body. A CRP test can help detect hidden inflammation and may be used with other tests to investigate infections, appendicitis, atherosclerosis, or chronic inflammatory disease.

Normal c-reactive protein levels are usually below 10 mg/L, although reference ranges can vary slightly by lab. Higher results may suggest mild inflammation, bacterial infection, severe infection, or sepsis, depending on the level and the person’s symptoms.

A high-sensitivity CRP test can also help estimate heart disease risk, including the risk of heart attack or stroke. Treatment for high c-reactive protein depends on the cause and may include further testing, lifestyle changes, hospitalization, or IV antibiotics when a serious infection is confirmed.

gloved hand holding tube of blood

Normal CRP levels

A C-reactive protein (CRP) level is generally considered normal when it is below 10 mg/L or 1 mg/dL. However, the reference range may vary slightly depending on the lab where the test was done.

Heart disease risk

Higher CRP levels may be linked to a higher risk of cardiovascular disease. In general, the following CRP values can help estimate a person’s risk of developing heart disease:

  • Very high risk: above 10 mg/L (1 mg/dL)

  • High risk: 2.0 mg/L (0.2 mg/dL)

  • Moderate risk: between 1.0 and 2.0 mg/L (0.1 and 0.2 mg/dL)

  • Low risk: less than 1.0 mg/L (0.1 mg/dL)

The result should be interpreted by a healthcare provider. To reach a diagnosis, it is important to review other tests as well, as this can help identify the cause of increased or decreased CRP levels more accurately.

What is a high-sensitivity CRP test?

A high-sensitivity CRP test may be ordered by a healthcare provider to help assess a person’s risk of cardiovascular problems, such as a heart attack or stroke.

This test is often used when a person has no symptoms or obvious signs of active infection or inflammation. It is more sensitive than a standard CRP test and can detect very small amounts of CRP in the blood.

If a person appears healthy but has elevated high-sensitivity CRP levels, this may suggest a higher risk of cardiovascular disease. According to the American Heart Association, high-sensitivity CRP is an inflammation marker linked to a higher risk of heart attack or stroke. A healthcare provider may recommend heart-healthy lifestyle changes, such as a balanced diet and regular exercise.

High CRP

High C-reactive protein (CRP) usually indicates an inflammatory or infectious process in the body. It may be a sign of a bacterial infection, cardiovascular disease, rheumatic disease, or even transplant rejection, for example.

CRP levels can indicate how severe the inflammation or infection may be:

  • CRP between 1.0 and 10.0 mg/L: usually indicates mild inflammation or minor infections, such as gingivitis, the flu, or a cold

  • CRP between 10.0 and 40.0 mg/L: may be a sign of a more moderate to serious infection, such as chickenpox, COVID-19, or other respiratory infections

  • CRP above 40 mg/L: usually indicates a bacterial infection

  • CRP above 200 mg/L: may indicate sepsis, a serious condition that can be life-threatening

An elevated CRP level can also be linked to chronic diseases. Because CRP alone cannot identify the exact condition, a healthcare provider may order other tests to find out what is causing the increase.

Low CRP

Low C-reactive protein (CRP) levels may be seen after significant weight loss, regular exercise, alcohol consumption, or the use of certain medications. A healthcare provider should review the result along with the person’s health history to understand what may be causing it.

What to do if CRP is high

After confirming high CRP levels, the doctor should review the results of any other tests that were ordered and evaluate the patient’s symptoms, medical history, and physical exam findings. Once the cause is identified, treatment can be started in a more targeted and specific way.

If the patient only has general discomfort and no other symptoms or specific risk factors, a healthcare provider may order additional tests to better understand the cause of the elevated CRP. Depending on the evaluation, this may include blood tests, imaging tests, or other exams to check for infections, inflammatory conditions, or, less commonly, cancer.

When CRP levels are above 200 mg/L and an infection is confirmed, the doctor may recommend hospitalization, especially if the infection is severe or there are signs of sepsis. According to the CDC, sepsis is a medical emergency that requires fast recognition and treatment. In these cases, antibiotics may be given through a vein.

CRP levels can begin to rise within 6 to 8 hours after inflammation or infection starts and often decrease when treatment is working. If CRP levels do not improve after 48 hours of antibiotics, or if symptoms worsen, the doctor may reassess the diagnosis and adjust the treatment plan.

Update History
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