C Reactive Protein (2024)


C-reactive protein (CRP) was discovered by Tillett and Francis in 1930. The name CRP arose because it was first identified as a substance in the serum of patients with acute inflammation that reacted with the "c" carbohydrate antigen of the capsule of pneumococcus.

CRP is a pentameric protein synthesized by the liver, whose levelrises in response toinflammation.CRP is an acute-phase reactant protein that is primarily induced by the IL-6 action on the gene responsible for the transcription of CRP during the acute phase of an inflammatory/infectious process. There is somequestion about whether dysregulation of the role of CRP in the clearance of apoptotic cells and cellular debris plays a role in the pathogenesis of systemic lupus erythematosus (SLE), but this has not been definitively demonstrated. It has been demonstrated to have someprotective properties in animal studies on lung tissue in alveolitis by reducing neutrophil-mediated damage to the alveoli and protein leakage into the lung.

CRP has both proinflammatoryand anti-inflammatory properties. It plays a role in the recognition and clearance of foreignpathogens and damaged cellsby binding to phosphocholine, phospholipids, histone, chromatin, and fibronectin. It can activate the classic complement pathway and also activate phagocytic cells via Fc receptors to expedite the removal of cellular debris and damaged or apoptotic cells and foreign pathogens.This can become pathologic, however, when it is activated by autoantibodies displaying the phosphocholine armin auto-immune processes, such asidiopathicthrombocytopenic purpura (ITP). It can also worsen tissue damage in certain cases by activation of the complement system and thus inflammatory cytokines.[1][2][3]

As compared to the erythrocyte sedimentation rate, which is an indirect test for inflammation, the levels of CRP rise and fall rapidly with the onset and removal of the inflammatory stimulus, respectively. Persistently elevated CRP levels can be seen in chronic inflammatory conditions such as chronic infections or inflammatory arthritides such as rheumatoid arthritis.

There are numerous causes of an elevated C-reactive protein. These include acute and chronic conditions, and these can be infectious or non-infectious in etiology. However, markedly elevated levels of CRP are most often associated with an infectious cause[4] (an example of pathogen-associated molecular pattern recognition). Trauma can also cause elevations in CRP (alarmin response). More modest elevations tend to be associated with a broader spectrum of etiologies, ranging from sleep disturbances to periodontal disease.

Specimen Collection

A blood specimen is taken froma peripheral venous draw. A phlebotomist performs the procedure in most cases. Thephlebotomistsecures a snug rubber band around the upper arm, and the patient pumps his or her fist several times. Thephlebotomistpalpates the vein to confirm the location and cleanses the area with an alcohol prep pad. Once the area air dries, the practitioner introduces a needle into the vein and draws a vial of blood. He or sheremoves the band from the patient's arm and then removes the needle and applies pressure to the venipuncture site until hemostasis occurs, usually within one minute. A bandage is applied over the site.

The patient's medications should be reviewed, as these can affect the outcome of the test. Fasting is not required before the blood draw. There are no special procedures required. Complications include oozing at the draw site, bruising or mild tenderness at the site, or veryrarely, infection at the venipuncture site.Other bodily fluids, such as synovial fluid, can be tested for in this manner but frequently are not.

Immunoassays and laser nephelometry are the methods to quantify CRP levels and are cheap, accurate, and fast. To detect lower levels of CRP (0.3 to 1.0 mg/L), high-sensitivity CRP methods are recommended as the usual CRP detection tests are less precise.High-sensitivity CRP only denotes the assay process used, allowing for detection of lower levels of CRP and not a different, or more specific, differential diagnosis.


This test is performed when the physician suspects acute or chronic inflammation (e.g., SLE or rheumatoid arthritis [RA]) or infection. The utility of the hs-CRP for cardiac screening is debatable.There is somecorrelation between cardiovascular risk and elevated hs-CRP, but the application of this is stillcontroversial especially given the poor specificity of this test, and it is currentlyundergoing more evaluation.[5][6][7]

Normal and Critical Findings

Lab values vary, and there is no standard at present. However, in general, the result is reported in either mg/dL or mg/L. Hs-CRP is usually reported in mg/dL.When used for cardiac risk stratification, hs-CRP levels less than 1 mg/dL are consideredlow risk. Levels between 1mg/dLand 3 mg/dL are considered a moderate risk, and a level greater than 3 mg/dL is consideredhigh risk for the development of cardiovascular disease.[8][9]

Interpretation of CRP levels:

Less than 0.3 mg/dL: Normal (level seen in most healthy adults).

0.3 to 1.0 mg/dL: Normal or minor elevation (can be seen in obesity, pregnancy, depression, diabetes, common cold, gingivitis, periodontitis, sedentary lifestyle, cigarette smoking, and genetic polymorphisms).

1.0 to 10.0 mg/dL: Moderate elevation (Systemic inflammation such as RA, SLE, or other autoimmune diseases, malignancies, myocardial infarction, pancreatitis, bronchitis).

More than 10.0 mg/dL: Marked elevation (Acute bacterial infections, viral infections, systemic vasculitis, major trauma).

More than 50.0 mg/dL: Severe elevation (Acute bacterial infections).

Interfering Factors

Certain medications, such as non-steroidal anti-inflammatory drugs (NSAIDs), will falsely decrease CRP levels. Statins, as well,have been known to reduce CRP levels falsely. Recent injury or illness can falsely elevate levels, particularly when using this test for cardiac risk stratification. Magnesium supplementation also can decrease CRP levels.

As mentioned above, mild elevations in CRP can be seen without any systemic or inflammatory disease. Females and elderly patients have higher levels of CRP. Obesity, insomnia, depression, smoking, and diabetes can all contribute to mild elevations in CRP, and the results shall be interpreted with caution in individuals with these comorbidities.


Given the highly variable causality of elevated CRP, marginal elevations in the CRP can be difficult to interpret and should not be used asan isolated test result interpreted as appropriate for the clinical picture. It is useful in suggesting infection versus inflammation if the levels are extremelyhigh, but levels between 1 mg/dL and 10 mg/dL can be difficult to interpret accurately. Chronic conditions, such as inflammatory arthritis or SLE, can make these levels elevated chronically, makingit harder to determine if there is any significance to an elevated hs-CRP level when using it as a predictive marker for cardiovascular disease.

Clinical Significance

Very high levels of CRP, greater than 50 mg/dL, are associated with bacterial infections about 90% of the time. In multiple studies, CRP has been used as a prognostic factor in acute and chronic infections, including hepatitis C, dengue, and malaria.[10][11][12]On the other hand, mild elevations may or may not be clinically relevant. Clinical correlation is strongly recommended while interpreting the results of the CRP test.



Cleland DA, Eranki AP. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Apr 23, 2023. Procalcitonin. [PubMed: 30969616]


Jungen MJ, Ter Meulen BC, van Osch T, Weinstein HC, Ostelo RWJG. Inflammatory biomarkers in patients with sciatica: a systematic review. BMC Musculoskelet Disord. 2019 Apr 09;20(1):156. [PMC free article: PMC6456959] [PubMed: 30967132]


Kramer NE, Cosgrove VE, Dunlap K, Subramaniapillai M, McIntyre RS, Suppes T. A clinical model for identifying an inflammatory phenotype in mood disorders. J Psychiatr Res. 2019 Jun;113:148-158. [PubMed: 30954775]


Vanderschueren S, Deeren D, Knockaert DC, Bobbaers H, Bossuyt X, Peetermans W. Extremely elevated C-reactive protein. Eur J Intern Med. 2006 Oct;17(6):430-3. [PubMed: 16962952]


Eschborn S, Weitkamp JH. Procalcitonin versus C-reactive protein: review of kinetics and performance for diagnosis of neonatal sepsis. J Perinatol. 2019 Jul;39(7):893-903. [PubMed: 30926891]


Darooghegi Mofrad M, Milajerdi A, Koohdani F, Surkan PJ, Azadbakht L. Garlic Supplementation Reduces Circulating C-reactive Protein, Tumor Necrosis Factor, and Interleukin-6 in Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials. J Nutr. 2019 Apr 01;149(4):605-618. [PubMed: 30949665]


Dick AG, Magill N, White TCH, Kokkinakis M, Norman-Taylor F. C-reactive protein: what to expect after bony hip surgery for nonambulatory children and adolescents with cerebral palsy. J Pediatr Orthop B. 2019 Jul;28(4):309-313. [PubMed: 30925527]


Lee Y, McKechnie T, Doumouras AG, Handler C, Eskicioglu C, Gmora S, Anvari M, Hong D. Diagnostic Value of C-Reactive Protein Levels in Postoperative Infectious Complications After Bariatric Surgery: a Systematic Review and Meta-Analysis. Obes Surg. 2019 Jul;29(7):2022-2029. [PubMed: 30895509]


Johns I, Moschonas KE, Medina J, Ossei-Gerning N, Kassianos G, Halcox JP. Risk classification in primary prevention of CVD according to QRISK2 and JBS3 'heart age', and prevalence of elevated high-sensitivity C reactive protein in the UK cohort of the EURIKA study. Open Heart. 2018;5(2):e000849. [PMC free article: PMC6269641] [PubMed: 30564373]


Bhardwaj N, Ahmed MZ, Sharma S, Nayak A, Anvikar AR, Pande V. C-reactive protein as a prognostic marker of Plasmodiumfalciparum malaria severity. J Vector Borne Dis. 2019 Apr-Jun;56(2):122-126. [PubMed: 31397387]


Vuong NL, Le Duyen HT, Lam PK, Tam DTH, Vinh Chau NV, Van Kinh N, Chanpheaktra N, Lum LCS, Pleités E, Jones NK, Simmons CP, Rosenberger K, Jaenisch T, Halleux C, Olliaro PL, Wills B, Yacoub S. C-reactive protein as a potential biomarker for disease progression in dengue: a multi-country observational study. BMC Med. 2020 Feb 17;18(1):35. [PMC free article: PMC7025413] [PubMed: 32063229]


de Souza Pires-Neto O, da Silva Graça Amoras E, Queiroz MAF, Demachki S, da Silva Conde SR, Ishak R, Cayres-Vallinoto IMV, Vallinoto ACR. Hepatic TLR4, MBL and CRP gene expression levels are associated with chronic hepatitis C. Infect Genet Evol. 2020 Jun;80:104200. [PubMed: 31962161]

Disclosure: Sara Nehring declares no relevant financial relationships with ineligible companies.

Disclosure: Amandeep Goyal declares no relevant financial relationships with ineligible companies.

Disclosure: Bhupendra Patel declares no relevant financial relationships with ineligible companies.

C Reactive Protein (2024)


What does it mean if CRP C is high? ›

A high CRP is more than 10mg/L. This shows that there is inflammation somewhere in your body. Other tests might be necessary to find out where or which specific illness or infection is causing the inflammation. If you are being treated for an infection or inflammation, your CRP levels should decrease.

What level of C-reactive protein is concerning? ›

C-reactive protein is measured in milligrams per liter (mg/L). Results equal to or greater than 8 mg/L or 10 mg/L are considered high. Range values vary depending on the lab doing the test. A high test result is a sign of inflammation.

What is an alarming CRP? ›

Generally, a CRP level of less than 10 mg/L is considered normal. CRP levels between 10 and 100 mg/L indicate mild to moderate inflammation, while levels above 100 mg/L indicate severe inflammation.

What infections cause high CRP? ›

Substantially raised CRP values are usually found in pneumonia,3-6 and a high CRP value has been shown to be a strong predictor for this disease in general practice. However, raised CRP values may also be found in uncomplicated viral respiratory infections, particularly those caused by influenza virus and adenovirus.

Should I be concerned if my CRP is high? ›

If your CRP test results reveal that you have high levels of CRP, it doesn't necessarily mean that you have a medical condition that needs treatment, especially if they're only slightly elevated. Several factors, such as smoking, recent injury and certain health conditions, can raise your CRP levels.

How do you treat high C-reactive protein? ›

There's no doubt that the very best way to lower CRP is through exercise, weight loss, and dietary control; of course, those are all proven already to lower vascular risk. There is a paper that came out in February comparing the Atkins diet, the Zone diet, the Weight Watchers diet, and the Ornish diet.

What cancers have high CRP? ›

Elevated CRP levels have been found to be associated with several cancers, including breast, lung, gastric, and colorectal cancer, hepatocellular carcinoma, and renal carcinoma (Roxburgh and McMillan, 2010; Wu et al., 2011).

What autoimmune disease causes high CRP? ›

A wide variety of inflammatory conditions can cause elevated CRP levels, including :
  • autoimmune conditions, including rheumatoid arthritis (RA), lupus, and certain types of inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis.
  • pericarditis, which is inflammation of the lining of the heart.

What level of CRP indicates arthritis? ›

Normal C-reactive protein (CRP) levels
C-reactive protein level (in milligrams per liter of blood) in adultsWhat it means
10.0–100.0moderately elevated, which signifies infection or an inflammatory condition such as rheumatoid arthritis (RA), Crohn's disease, or lupus
4 more rows

Is CRP a tumor marker? ›

Elevated CRP levels (> 10 μg/ml) are associated with active, advanced cancer disease.

How to bring CRP levels down? ›

Limiting or avoiding inflammatory foods like refined carbohydrates, fried foods, red meat and processed meat can help reduce CRP. Instead, focus on eating more anti-inflammatory foods like leafy greens, nuts, fatty fish and whole grains.

What medications affect C-reactive protein? ›

Cyclooxygenase inhibitors (aspirin, rofecoxib, celecoxib), platelet aggregation inhibitors (clopidogrel, abciximab), lipid lowering agents (statins, ezetimibe, fenofibrate, niacin, diets), beta-adrenoreceptor antagonists and antioxidants (vitamin E), as well as angiotensin converting enzyme (ACE) inhibitors (ramipril, ...

What foods should you avoid if you have high CRP? ›

Avoid Foods That Cause Inflammation: Processed meals, sugary snacks, and excessive consumption of red meat can all contribute to inflammation. Limiting these foods in your diet can help lower CRP levels.

Can dehydration cause high CRP levels? ›

This is particularly concerning as high CRP levels, potentially exacerbated by factors like dehydration and certain dietary habits, can indicate a dangerous level of inflammation in the body.

What are the symptoms of C reactive protein? ›

Or it may be a potentially life-threatening condition called sepsis or blood poisoning. Symptoms of sepsis may include fever and chills, headache, pain, nausea, vomiting, confusion, rash, and shortness of breath. The level of CRP in your blood goes up within a few hours of a serious infection.

What CRP level indicates Crohn's disease? ›

Conclusion: CRP elevation in Inflammatory Bowel Disease is associated with active disease determined endoscopically, histologically, or radiographically. In both CD and UC, a CRP > 2.0 mg/dL predicts findings of active ileal disease at ileocolonoscopy.

What does it mean when your inflammatory markers are elevated? ›

What does a raised inflammatory marker mean? Medical decisions will not be made solely on the results of an inflammatory marker test. Abnormal results suggest inflammation, but don't identify the cause: it might be as simple as a viral infection, or as serious as cancer.

What does C-reactive protein cardiac mean? ›

Your level of C-reactive protein can be an indicator of how at risk you are for developing cardiovascular problems. This is because the development of atherosclerosis (laying down of cholesterol inside the blood vessel walls) is associated with inflammation within the vessel walls.

Top Articles
Latest Posts
Article information

Author: Cheryll Lueilwitz

Last Updated:

Views: 6664

Rating: 4.3 / 5 (54 voted)

Reviews: 85% of readers found this page helpful

Author information

Name: Cheryll Lueilwitz

Birthday: 1997-12-23

Address: 4653 O'Kon Hill, Lake Juanstad, AR 65469

Phone: +494124489301

Job: Marketing Representative

Hobby: Reading, Ice skating, Foraging, BASE jumping, Hiking, Skateboarding, Kayaking

Introduction: My name is Cheryll Lueilwitz, I am a sparkling, clean, super, lucky, joyous, outstanding, lucky person who loves writing and wants to share my knowledge and understanding with you.