C-reactive protein (CRP) is one of the many proteins which can be found in human blood at varying levels, depending on someone's health. Evaluating levels of C-reactive protein may be a part of diagnosis of disease, and monitoring of CRP levels can also play a role in determining how well a patient is responding to a particular medication. Laboratories which handle blood can determine the level of protein in the blood by using a special test which may be used upon a doctor's request.
This protein is produced by the liver and the fat cells in the body. The body makes this kind of protein in response to infection, which means that elevated CRP levels can suggest a systemic infection. The concentration in the blood tends to rise with the severity of the infection, reaching a peak and then declining as the body breaks the protein down once the infection has been dealt with. Medications used to manage systemic infections and inflammations should cause a decrease in CRP levels.
Several things beyond infection can alter the levels of CRP in the blood. Pregnant women and women on hormonal birth control tend to have higher levels, as do people who consume a high amount of dietary fat. Liver disease can change CRP levels, since the liver is a major producer of this protein. When abnormal C-reactive protein levels are found during a blood screening, the patient may be interviewed to rule out these causes.
Studies on this protein have suggested that certain diseases can leave telltale sugars bound to CRP, sort of like fingerprints. Theoretically, it should be possible to test the protein for presence of particular sugars which could be used to identify a specific disease, although this would require very specialized equipment. More generally, a high level of this protein suggests that a patient is coping with infection somewhere in his or her body.
Naturally, CRP is present in trace amounts in the blood. Using highly sensitive tests, doctors can look for the slightly elevated levels which have been linked with high blood pressure, heart disease, and diabetes. The presence of higher levels can indicate that a patient is at greater risk of developing these medical conditions. If a patient takes a highly sensitive test which does reveal high levels, a doctor may make recommendations to help minimize the patient's risk, such as making changes to diet and exercise programs.