C-reactive protein (CRP): what does it mean high or low?

Not infrequently are the times when people need to have tests to check for the presence of infectious or inflammatory disorders.

For this, it is common to use the ESR test (hemosedimentation speed), created in 1897. This test can be performed through a simple blood count and provides analysis of changes in the body – from colds to problems such as arthritis .

In addition to the VHS exam, many doctors currently opt for the PCR (C-reactive protein) exam, which works in the same way. See more information:


What is C-reactive protein?

C-reactive protein, commonly known as CRP , is an acute phase protein (produced by the liver) and, therefore, undergoes increases in its concentration when there is an indication of infections or inflammations in the body.

Therefore, a PCR exam can be ordered in order to check or see if there is really an inflammatory or infectious process taking place in the body. This considering that C-reactive protein is a highly sensitive indicator of such processes.

Then, with the exam it is possible to know if the CRP value is normal or with changes – it may be high, low or ultra sensitive.

However, it is worth noting that changes in CRP levels start about 4 to 6 hours after the stimulus in the body, reaching its peak between 36 and 50 hours. That is, it is not an immediate response.

In addition, even after a single stimulus (such as trauma or surgery), it can take several days to return to normal levels.

These questions reinforce that, despite its safety and accuracy, the C-reactive protein test is not highly specific and has limitations. Whereas, alone, it is not enough for an accurate diagnosis.

But how does this test work and what can it detect? Check out:

What is it for: what is the function of C-reactive protein?

As mentioned, the CRP test is performed mainly in order to detect possible infections or inflammations in the body. Basically, it is requested by the medical team in 3 situations:

  • In order to find out if there is any inflammation or infection in the body;
  • To monitor inflammation;
  • To measure, indirectly, a person’s cardiac risk.

The level of C-reactive protein is measured by means of a common blood count (blood test ) – which requires a mandatory fast of 8 hours and, in the case of lactating women, an interval between feedings.

But, in addition to analyzing infectious and inflammatory disorders, this test can also help to detect diseases and problems such as:

  • Lupus;
  • Rheumatoid arthritis ;
  • Acute pancreatitis;
  • Appendicitis;
  • Lymphoma;
  • Myocardial infarction;
  • Cerebrovascular accident ( CVA );
  • Sepsis (generalized infection).

In addition, it is also common to be asked – for example – after performing a surgical procedure, to ensure that there has been no infection after the surgery.

It is worth mentioning that this test is not indicated in order to check for possible infections or inflammations in asymptomatic patients (people who do not have previous evidence of any pathology).

However, there is an exception when it is desired to stratify risk for cardiovascular diseases. That is, when the doctor requests the exam in order to classify the risk of the patient to have cardiovascular problems – such as stroke or heart attack.

In this case, the following indices can be taken into account:

  • CRP above 3.0 mg / L – high risk;
  • CRP between 1.0 and 3.0 mg / L – medium risk;
  • CRP less than 1.0 mg / L – low risk.

Bearing in mind that even having reference values, they can vary according to each laboratory. So, it is necessary to take into account the values ​​defined by the laboratory in question and it is essential that a doctor does the evaluation of the exam.

What is the ultrasensitive C-reactive protein test?

There are two different types of tests for PCR. The PCR ultrasensitive dosing method measures exactly the same protein as the standard test. However, as the name suggests, its sensitivity is greater and therefore it is able to detect much lower concentrations of C-reactive protein.

This approach is necessary and most useful in cases where it is desired to measure the risks of a cardiovascular problem. So, in this case, the PCR exam acts preventively.

Thus, it is considered that CRP (ultrasensitive C-reactive protein) acts in the evaluation process, before one of these health problems is encountered.

There are even more specific studies underway in order to better understand its role in cardiovascular disorders – which could change the guidelines on its use in screening and treatment decisions.

In addition to the recurrent cardiovascular problems (stroke, heart attack , etc.) this test also assesses the risk of developing coronary artery disease – a condition in which the heart arteries are narrowed, which can lead to a heart attack.

In some cases, it can also be used to measure the chances of a new heart attack in patients who have previously suffered from this problem.

Is CRP specific to predict heart disease?

No . As mentioned, the CRP test is more sensitive than the traditional CRP test, so it can measure much lower concentrations of C-reactive protein.

In addition to being used to predict cardiovascular problems, there is also new research that suggests that changes in CRP may be associated with other diseases – such as colon cancer , diabetes complications and obesity .

What are the precautions and guidelines for taking the exam?

In general, the care to perform the PCR exam involves following the medical and laboratory guidelines in question. This is because, among the recommendations, is the need to fast before collecting blood.

In addition, when the person is going to have an ultrasensitive C-reactive protein test, in order to check the risk of coronary heart disease or heart attack, he must be healthy (without recent injuries, infections or inflammations).

This is so that the test does not suffer momentary interference.

A warning is also needed for people suffering from chronic inflammation (such as arthritis), as their CRP levels are naturally already very high.

Since CRP and CRP tests measure the same molecule, these people should not have CRP levels measured.

What is the normal value of C-reactive protein?

According to experts, the reference value (normal value) of C-reactive protein is 3mg / L (0.3 mg / dL) or less – it may vary depending on the laboratory.

Considering that the PCR exam, in general, is not requested in asymptomatic patients, but for those who already show signs of some pathology, the results of the exam can be useful for medical diagnosis.

In this sense, studies show that mild inflammation or viral infections usually result in elevations in CRP between 10mg / L to 40mg / L.

On the other hand, when there are more serious infections in the body, the values ​​are usually between 40mg / L and 200mg / L.

Do high C-reactive protein have symptoms?

The symptoms of elevated CRP can vary depending on the condition or disease that is causing the levels of C-reactive protein in the body to increase.

But in general, some of the possible symptoms are:

  • Fever ;
  • Pains;
  • Nausea, loss of appetite and indigestion;
  • Acceleration in heart rate;
  • Sweating, chills or tremors;
  • Dry lips and skin.

It is possible to notice that the symptoms are quite characteristic of inflammatory and infectious processes. Like, for example, fever and its complications (dry lips, sweating, etc.).

Thus, it is worth remembering that the C-reactive protein is a consequence of the changes that are occurring in the body and, therefore, the symptoms in general are related to inflammation and not to CRP itself.

What can be high C-reactive protein in a baby?

As in adults, when there are changes in the levels of C-reactive protein in infants or children, this is a sign that an inflammatory or infectious process may be occurring in the body.

It is common for pediatricians to request the PCR exam when the child already has some indication of these conditions – such as fever, for example.

In case of high CRP, keep in mind that this test alone is not conclusive. Then, follow the directions of the pediatrician regarding the necessary care and treatments.

What does the measurement of C-reactive protein mean?

As we saw in a previous topic, the values ​​of C-reactive protein are variable and understanding these variations is of paramount importance.

This considering that the different levels of CRP can indicate problems or, when within the normal range, the good health of the organism. Check out:


C-reactive protein is produced by the liver and is naturally present in the blood of all people. However, for the organism to be healthy, it must be at a normal level.

When this does not happen and the CRP dosages are high, it is an indication of possible inflammatory or infectious processes. In addition to demonstrating the greatest risk of developing cardiovascular disease.

In the case of CRP between 0.1 mg / dL and 0.3 mg / dL, the risks are moderate. When it is constantly above 0.3mg / dL, it is understood that the chances are high that the person will develop cardiovascular problems.

In addition, regarding the high levels of CRP in cases of inflammation and infections, some studies indicate that, in general, the following data can be taken as a parameter:

  • Mild inflammations and viral infections – increase CRP to 10mg / L to 40mg / L;
  • Severe inflammation and bacterial infections – raise CRP to 40mg / L to 200mg / L.

Even so, the need for medical monitoring to analyze the tests is reinforced.

In some cases, the values ​​may also be high in cases of necrosis (tissue death), which is common when an infarction occurs, for example.

It is also worth noting that the increase in C-reactive protein levels is not always related to pathologies, as other factors can also interfere in the results (such as pregnancy or the use of some medications).

Therefore, despite being an accurate and safe test, it is not specific enough to diagnose diseases – considering that the values ​​may be high in the presence of any inflammatory process or be altered for other reasons.

Thus, it is always used in conjunction with other tests to provide a correct diagnosis of the source of the problem.


Low C-reactive protein values ​​generally indicate that the body is free of infection or inflammation.

It is also worth noting that when there is constancy in the low levels of CRP, there is less risk that the person will suffer from cardiovascular problems (such as stroke and heart attack).

However, as mentioned in the previous topic, this is not a highly specific exam. Therefore, diseases can be active without causing changes in the levels of this protein.

What does non-reactive C-reactive protein mean?

When the results of the C-reactive protein test indicate “non-reactive”, it means that the CRP levels in the body are within normal limits.

This depends on the type of exam adopted by the laboratory. Those that show results in numbers are called quantitative. But both are equally effective and work with the same methodologies.

That is, non-reactive indicates that there are no changes or signs of inflammatory processes.

Factors that can affect the result of the PCR exam

Some experts reinforce that a change in the result of the PCR test is not necessarily related to a health problem.

This is because some factors can change the amount of C-reactive protein in the blood and, consequently, affect the results. Some of the ones that increase the indexes are:

  • Hormone replacement therapy;
  • Pregnancy;
  • Intense physical exercise;
  • Use of intrauterine device ( IUD ).

In contrast, the administration of some medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) or statins (drugs that lower cholesterol), can lower CRP levels – as they help to reduce inflammatory processes.

The PCR exam is an important step during the analysis and diagnosis of inflammatory and infectious processes in the body. It is worth remembering that even knowing your reference values, an individual analysis is never recommended – that is, always wait for the medical opinion.

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