Normal CRP level in the blood

Each laboratory must establish its own normal ranges for C-reactive protein (CRP) in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

There are two types of CRP assays. The standard one measures a wide range of CRP levels to include those found in patients with inflammation or acute infections. This is the test explained here. The second type is a high-sensitivity CRP (hs-CRP) assay. The hs-CRP is useful for assessment of risk for developing myocardial infarction in patients presenting with acute coronary syndromes.

The CRP increases after the first trimester of pregnancy and persists until delivery. For this reason, it is necessary to follow the ranges of each laboratory depending on the week of pregnancy.

The upper limit is age-dependent. It can be estimated along the following formula: Upper limit (mg/dl) equals (age in years)/50 for men and (age in years/50) + 0.6 for women.

The C-reactive protein (CRP) is an acute-phase protein that is synthesized in the liver. The C-reactive protein (CRP) increases with inflammatory processes and with infections.

This protein is virtually absent from the blood serum of healthy persons. However, its presence in the blood increases within hours of an acute injury or the onset of inflammation and may reach as high as 20 times the normal levels.

Therefore, it is believed that the C-reactive protein (CRP) plays a key role in the innate immune system with anti-inflammatory effects.

The presence of C-reactive protein (CRP) in the blood is a marker of inflammation. CRP increases in the bloodstream in response to any inflammatory process.

Levels of CRP can increase dramatically after severe trauma, bacterial infection, inflammation, surgery, or neoplastic proliferation.

Measurement of CRP in the blood has been used historically to:

• Assess activity of inflammatory disease: CRP becomes negative with successful treatment and indicates that the inflammation has subside. If not, it suggests a poor prognosis. It is used in this way to monitor, for example, the rheumatoid arthritis evolution.
• Detect infections after surgery in postoperative surveillance: CRP levels invariably rise after major surgery but fall to normal within 7–10 days. The absence of this fall is indicative of possible septic or inflammatory postoperative complications.
• Detect transplant rejection, for example, in kidney transplants.
• Monitor inflammatory processes and treatment with anti-inflammatory medication (they should reduce CRP levels).

CRP is not specific for any disease and it is only a help for diagnosis because there are multiple inflammatory diseases and bacterial infections where there is an increase CRP values in the blood. Further tests are necessary for a definitive diagnosis.

Apart from indicating inflammatory disorders, CRP measurement helps in differential diagnosis, in the management of neonatal septicemia and meningitis where standard microbiological investigations are difficult.

There are also some non-inflammatory diseases related to metabolism that may increase CRP in the blood, such as obesity, tobacco, diabetes, high blood pressure, lack of sleep, fatigue or depression.

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in mg/dl. They are an example of a healthy man of about 40 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.