CRP or C-Reactive Protein Normal, High, Low: When to Worry?

C-reactive protein (CRP) is a biological marker of inflammation; it is a protein that appears in the blood when an acute infection is present in the body. Its level increases rapidly after the onset of inflammation. Its measurement, therefore, provides a reliable indication at a given time of an individual’s health status and the effectiveness of a treatment.

Definition: What is C-reactive protein, or CRP?

CRP is a protein synthesized by liver cells, hepatocytes, in response to acute inflammation in the body. When the body is affected by inflammation or infection, CRP levels rise rapidly within hours. Therefore, the higher the CRP levels, the more severe the infection or inflammation.

In short, C-reactive protein is one of the proteins produced in the acute phase of infection or inflammation; it is an immune response.

Its concentration will peak within 36 to 48 hours of the onset of inflammation or infection. It then declines rapidly once the condition is treated. Its role is therefore to be a stable biological marker for detecting inflammation or infection at an early stage. CRP appears in all inflammatory processes and does not cross the placenta.

CRP Analysis: What is it?

C-reactive protein testing is prescribed when inflammation or infection is suspected. Its level will help assess the activity of the inflammation. Generally, CRP is a protein whose level changes rapidly after the onset of infection, even before other symptoms, such as fever, appear.

The dosage of this protein may be prescribed in other situations:

To assess possible infections and the inflammation status of patients.
To monitor the effectiveness of a treatment, noting that the patients’ CRP decreases;
For patients who have just undergone a surgery for which complications are suspected;
Diagnose and monitor the condition of a chronic inflammatory disease in patients, and monitor their treatment.

Standard exam

Standard C-reactive protein testing is most often indicated as part of an infectious blood workup. In this situation, additional testing to identify the cause of an abnormal level will be necessary, since the CRP level is only an indicator.

Blood test for hs-CRP

High-sensitivity CRP, or hs-CRP, is measured to assess cardiovascular risk. This test is often supplemented by a blood lipid profile, which measures total cholesterol and triglyceride levels.

What is a CRP blood test?

The sample is taken by taking venous blood, usually from the crook of the elbow. A blood sample will be taken and collected in a collection tube that may contain an anticoagulant. The results are available fairly quickly, generally within 24 hours of collection. The result is available within a few minutes when using a remote biology machine.

Other ways to assess CRP are available. It can also be collected from cerebrospinal fluid ( lumbar puncture ), ascites (abdominal puncture), and synovial fluid (joint puncture).

Unlike blood tests performed by a nurse or lab technician, these procedures will be performed by appointment only by a doctor. These types of samples are exceptional, as they are performed on patients suffering from progressive inflammation of the spinal cord, liver, and joints.

Normal value of CRP dosage

To have a blood sample taken, you will need to go to the medical analysis laboratory closest to you, with your prescription, your Vitale card, and your mutual insurance card.

In the absence of inflammation, the normal value of a normal C-reactive protein test should be less than 6 mg/L (< 6 mg/L). It may be slightly higher than this figure and remain normal in overweight people or smokers.

Is it necessary to fast for CRP?

Fasting is not necessary for CRP, but be aware that other factors added by your doctor may require it.

Also, remember to report any medication or other intake (dietary supplements, etc.) that could affect the results. The blood sample will be taken on-site and then analyzed by laboratory technicians and a biological physician.

Why is my CRP level high?

A high level of CRP in the blood can be a sign of :

of a bacterial or viral infection, but also meningitis or septicemia;
of a myocardial infarction(ischemic necrosis);
of cancer (Hodgkin, carcinoma, lymphoma, sarcoma);
from trauma (burns, surgery);
of an inflammatory or autoimmune disease (rheumatoid arthritis, chronic arthritis, ankylosing spondylitis, Behçet’s syndrome, Reiter’s disease, Crohn’s disease, vasculitis, inflammatory rheumatism, acute).

In all cases, it is the doctor who will have access to your results and interpret them based on other parameters of your health. In the event of a high CRP result, the doctor will have to carry out other tests and an additional blood test in order to find the cause(s) of the development of this inflammation and make a diagnosis.

Possible variations in CRP

The viral diseases: the CRP level in children will be less than 20 mg/L and 50 mg/L in adults.
THEsystemic diseases in systemic lupus erythematosus (SLE) and ulcerative colitis (UC), CRP is low, less than 30 mg/L (< 30 mg/L). Its increase may be linked to a bacterial superinfection. To determine this, the doctor will prescribe other tests.

Can stress affect CRP levels?

Chronic stress is known to promote inflammation in the body. Since CRP is a marker of inflammation, its levels can be increased in diseases linked to low-grade inflammation, such as obesity, cognitive decline, asthma, respiratory diseases (COVID-19, bronchitis, etc.), or osteoporosis.

What are the symptoms of high CRP?

Symptoms of elevated CRP levels vary and depend on the cause of the increase. Here are some common examples:

In case of viral or bacterial infection: fever, chills, fatigue, headache, body aches, and symptoms correspond to the infected organ (cough in case of respiratory infection);
In case of inflammation: inflammatory signs such as skin lesions or joint pain;
Cardiovascular signs: dizziness, numbness on one side of the body, shortness of breath, heart palpitations, breathing difficulties;
Symptoms of being overweight: exertional dyspnea, muscle weakness, daytime sleepiness, sleep apnea…

If you experience any of these symptoms, do not hesitate to make an appointment with your doctor.

Low CRP levels

Low CRP values may be associated with cardiovascular disease.- CRP values above 2 mg/L are associated with an increased risk of myocardial infarction or stroke.- A CRP value above 3.5 mg/L in a person with unstable angina ( angina pectoris ) is associated with a risk of coronary heart disease.

Is it serious to have high CRP? What level is worrisome?

A CRP level above 6 mg/L should be monitored by a doctor. It may be due to a minor, mild infection, such as a bacterial infection, which can easily be treated with antibiotics. However, if CRP levels remain elevated, further testing will be required to determine a diagnosis. Finally, CRP is a test used to assess the effectiveness of a treatment: when the treatment is effective, the decrease in CRP levels can be observed in each blood test result.

How to lower CRP levels?

Treatment will be implemented based on the cause, which is why blood work and additional tests may be necessary. In the case of a bacterial infection, the doctor will prescribe antibiotics, which will quickly return your values to normal. In the case of a viral infection, you will need a little patience and rest.

To remember

CRP is an indicator; it is commonly prescribed on a blood test order as soon as the doctor suspects an infection.
It can also be used to monitor the progress of a disease under treatment and adjust it if necessary. If CRP increases, it is a consequence of the inflammation or infection present.
This is why the level alone does not make a diagnosis. It does not determine the cause of the inflammation or infection; for this, the doctor will have to prescribe additional tests or examinations, or even treatment.