C-Reactive Protein (CRP) Test

What is C-Reactive Protein (CRP) Test

C-Reactive Protein (CRP) Test is a blood test that measures the C-Reactive Protein (CRP) level in the blood. C-Reactive Protein (CRP) is a protein that the liver produces. From the liver, the protein goes to the blood.

Usually in the normal condition, the CRP levels in the blood is low, but during inflammation due to any cause, production of CRP increases, as a result, C-Reactive protein level in blood also increases.

C-Reactive Protein (CRP) Test Purpose

Purpose of C-Reactive Protein Test are the following

  1. To detect if any inflammation is present in the body or not
  2. To monitor the progress of inflammation
  3. To know if there is any severe infection
  4. To determine the chance to develop sepsis, a life -threatening condition
  5. To know the overall health status of the patient
  6. To know the outcome of treatment, in case of any inflammation

C-Reactive Protein (CRP) Test Importance

C- Reactive Protein Test is done if there is suspect of presence of any inflammation, be it known or unknown. The inflammations that are most commonly seen are

  1. Fungal infection
  2. Bacterial Infection
  3. Autoimmune disease such as lupus, rheumatoid arthritis
  4. Inflammatory bowel disease that causes swelling, bleeding in the intestines
  5. Bone infection such as osteomyelitis

So, the importance of C-Reactive Protein Test are the following

  1. To determine the severity of inflammation based on the C-Reactive Protein Level in the blood
  2. To know whether a person is at increased risk of heart attack within the next 10 years
  3. To determine the risk of developing coronary artery disease. This is of special importance who have a family history of heart and blood vessel diseases.
  4. To evaluate the risk of second heart attack

Why Do I Need a C-Reactive Protein (CRP) Test

You need a C-Reactive Protein Test if you have the following symptoms

1. Fever

2. Nausea, vomiting

3. Chills

4. Headache

5. Rapid breathing

6. Rapid or irregular heart rate

7. Swelling, redness, pain in any area

If you have a diagnosed inflammation due to any condition, or you have chronic disease, then C-Reactive Protein level helps to monitor the response towards treatment. C-Reactive Protein levels increase or decrease based on the severity of inflammation. If it is seen that C-Reactive Protein level decreases after treatment, it simply means that inflammation has decreased, so the treatment for inflammation is working.

C-Reactive Protein (CRP) Test Types

C-Reactive Protein Test is of two types

1. A standard CRP test

2. A high-sensitivity C-reactive protein (hs-CRP) test.

High sensitivity C reactive protein test is more sensitive than standard  C- Reactive Protein (CRP) test. So, it means that the high-sensitivity test can detect slight increases within the normal range of standard CRP levels.

High levels of high sensitivity C-Reactive Protein (hs-CRP) indicates the risk of developing coronary artery diseases and also indicates the chances of heart attack.

C-Reactive Protein (CRP) Test Procedure

C-reactive protein test is a routine blood test just like other blood tests such as MCV blood test, ESR blood test, RBC blood test, WBC blood test, Hemoglobin test,etc. For this test, blood is drawn from vein (preferably vein of the arm). Based on this blood sample, test results are prepared.

Usually this test requires no special precautions. But very strenuous exercise such as long run, intense weight training, etc. can lead to sudden increase of C-Reactive Protein level. So, it is advised not to do strenuous activities before the test.

Some medicines, supplements, herbal products can alter the test results. So, always tell your doctor about the medicines, supplements, herbal products you are using, before going for the test.

C-Reactive Protein (CRP) Test Results

C-Reactive Protein Test results are given as milligrams per litre (mg/L).

The normal level of standard C-Reactive Protein are less than 10 mg/L.

The high level of C-Reactive Protein are equal to or greater than 10 mg/dL.

A high C-Reactive Protein level indicates presence of acute inflammation due to any reason such as infection, autoimmune disease, injury, chronic disease, etc.

hs-CRP level: If the hs-CRP level is less than 2 mg/L, then there is lower risk of heart disease.

If the hs-CRP level is equal to or more than 2 mg/L, then there is higher risk of heart disease.

CRP levels in blood vary with time. So, repeat tests are needed for the risk assessment of coronary artery disease. Two tests are done in two weeks apart. Now, the average of two hs-CRP tests value are taken. If it is seen that the averahe value is more than 2 mg/L, it usually indicates higher risk of heart attack.

It is also important to note that there are many risk factors of coronary artery disease and hs-CRP is one of those risk factors. So, presence of high hs-CRP does not definitely mean that you will develop a heart disease. Other tests such as lipid profile test, etc. are also needed to determine the overall risk to develop a heart disease.

C-Reactive Protein (CRP) Test Drawbacks

The drawbacks of C-Reactive Protein test are the following

  1. This test does not give any clue about the site where the inflammation is present
  2. This test does not give any clue about how long the inflammation is present if there is no previous test result. One can compare the two test results done in different time periods, but it does not mean that the inflammation is absent or present persistently. CRP level varies with time based on inflammation, so one can get good idea about acute inflammation.


  1. Lehninger Principles of Biochemistry: International Edition
  2. Guyton and Hall Textbook of Medical Physiology
  3. Harrison’s Principles of Internal Medicine 20th edition
  4. Goldman-Cecil Medicine
  5. Davidson’s Principles and Practice of Medicine 23rd edition

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