C-Reactive Protein (CRP) Test: Ranges, Levels and Purpose (original) (raw)
- Introduction
- Signs
- Elevated Levels
- Normal Levels
- Test
- Indication
- Treatment
- How to Lower
- Heart Disease
- Heart Disease
- Heart Attack/Stroke
- FAQs
What is C-reactive protein (CRP)?
Diagram of healthy and unhealthy ranges for C-reactive protein (CRP)
- C-reactive protein (CRP) is a blood test marker for inflammation in the body. CRP is produced in the liver and its level is measured by testing the blood.
- CRP is classified as an acute phase reactant, which means that its levels will rise in response to acute inflammation. The acute phase reactant levels rise in the presence of inflammatory proteins called cytokines.
- Other common acute phase reactants include the erythrocyte sedimentation rate (ESR) and blood platelet count.
- A CRP blood test helps determine whether your body has inflammation and measures its level. However, a CRP blood test cannot identify the cause of inflammation or the exact location of the inflammation.
What are the symptoms and signs of high (elevated) C-reactive protein levels?
There are no signs or symptoms that are specific for an elevated C-reactive protein level, as CRP is a marker of inflammation rather than a direct cause of symptoms. Signs or symptoms, if present, would depend on the underlying inflammatory condition that is the cause of the elevated CRP level. Some of the symptoms and signs for which a CRP blood test may be indicated are as follows:
- Fever and chills
- Headache
- Pain
- Nausea
- Vomiting
- Confusion
- Rash
- Shortness of breath
- Rapid breathing
- Rapid heart rate
- Joint swelling and pain
- Morning stiffness
- Tiredness
- Weight loss
- Low-grade fevers
What does it mean to have elevated C-reactive protein levels in the blood?
In general, the main causes of increased CRP and other markers of inflammation are a variety of conditions, including:
- burns,
- trauma,
- infections, such as pneumonia or tuberculosis,
- heart attack,
- chronic inflammatory diseases such as lupus, vasculitis, or rheumatoid arthritis,
- inflammatory bowel disease, and
- certain cancers.
Elevated C-reactive protein levels in the blood indicate some inflammation in the body. High levels of C-reactive protein may also be found during pregnancy or while using birth control pills. The results of the C-reactive protein test can be interpreted as follows:
Moderate elevation: If your CRP blood test reveals a level between 1 and 10 milligrams per deciliter (mg/dL), it could indicate:
- Heart attack
- Pancreatitis
- Bronchitis
- Bodily inflammation from autoimmune diseases such as rheumatoid arthritis or lupus
Marked elevation: If the CRP blood test reveals CRP levels between 10 and 50 mg/dL, it could indicate:
- Acute bacterial infections
- Viral infections
- Systemic vasculitis
- Major trauma
Severe elevation: CRP levels above 50 mg/dL could be linked to bacterial, severe viral, and parasitic infections, including:
- Meningitis
- Bacterial sepsis
- Hepatitis C
- Dengue
- Malaria
What are the normal and elevated ranges for C-reactive protein?
C-reactive protein is a marker of inflammation and is typically not detected in the blood unless some degree of inflammation is present in the body.
The CRP normal range may vary from lab to lab. However, the most accepted normal range is typically less than 0.3 mg/dL. Elevated levels of CRP may indicate inflammation. C-reactive protein high levels, typically ranging from 10 to 50 mg/dL, suggest moderate inflammation. Severe elevation of CRP, usually above 50 mg/dL, is seen in conditions such as severe bacterial infections (such as sepsis), major trauma, or inflammatory diseases such as vasculitis.
How are normal and elevated C-reactive protein levels measured?
C-reactive protein is a marker of inflammation and is typically not detected in the blood unless some degree of inflammation is present in the body.
- CRP measurement is made using a blood sample from a vein. The sample is then taken to a laboratory and analyzed.
- The traditional CRP measurement is often used to detect inflammation in the body. Your health care provider may order a C-reactive protein test to check for flare-ups of inflammatory diseases such as rheumatoid arthritis, lupus, or vasculitis or to monitor whether anti-inflammatory medications are working to treat a disease or condition. To measure the CRP levels, the physician may use immunoassay or laser nephelometry, which are cheap, accurate, and fast.
- Currently, a more highly sensitive measurement to detect CRP is used for cardiovascular risk assessment. This high-sensitive C-reactive protein is termed hs-CRP. An hs-CRP blood test can detect lower levels of CRP (0.3 to 1 mg/dL), which cannot be detected by usual CRP blood tests.
- Because measuring CRP levels at any point in time may be influenced by any infection or inflammation in the body, one-time measurement is generally not regarded as an adequate predictor of cardiovascular risk. Therefore, the U.S. Centers for Disease Control and Prevention (CDC) recommends checking two separate CRP levels approximately two weeks apart and using the average number of the two readings for cardiovascular risk assessment and screening purposes.
It's important to note that CRP blood tests should not be performed on a regular basis. Avoid taking a CRP test if you have an active infection or inflammation, such as a cold or the flu, as these conditions can temporarily elevate CRP levels.
When should you have C-reactive protein blood levels tested?
Checking the CRP level for the entire adult population is not recommended. Some experts recommend checking the serum CRP level routinely along with the cholesterol level; however, this is not widely accepted. Ideally, for cardiac risk testing, it is advisable to use the average of two separate CRP levels drawn two weeks apart.
More importantly, the CRP level can provide additional information about an individual's cardiovascular risk in conjunction with other known cardiac risk factors, such as:
- diabetes mellitus,
- high blood pressure,
- high cholesterol,
- obesity,
- age, and
- smoking cigarettes.
A CRP test may be needed when a person experiences the following symptoms:
- Fever and chills
- Headache
- Pain
- Nausea
- Vomiting
- Confusion
- Rash
- Shortness of breath
QUESTION In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer
What is the treatment for elevated C-reactive protein blood levels?
The treatment of an elevated CRP in the context of cardiovascular disease, in and of itself, may be meaningless. Instead, appropriate treatment and prevention of the underlying risks and conditions need to be the primary focus of cardiovascular risk reduction.
The most effective and reliable ways to reduce many cardiac risk factors are:
- regular exercise,
- a balanced diet, and
- cigarette smoking cessation.
Individuals with elevated cholesterol levels who do not reach their target cholesterol level may consider:
- diet modifications,
- exercise, and
- cholesterol-lowering medication.
People with elevated C-reactive protein levels may be advised by their treating doctors. Statin drugs (such as simvastatin [Zocor], atorvastatin [Lipitor], etc.) are at the forefront of the recommended cholesterol-lowering agents. Lowering of CRP may be seen with the use of statin drugs even without significant improvement of the cholesterol profile. Research has shown that nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen, may be used to reduce CRP levels. Apart from NSAIDs, antidiabetic agents, angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARBs), antiplatelet agents, vitamin E, and beta-adrenoreceptor antagonists also lower CRP levels in the blood.
Reduction of CRP level has also been noted in individuals with known cardiovascular disease who begin aspirin therapy. In those without known cardiovascular disease or significant risk factors for it, aspirin use is not generally recommended. Some diabetic medications (thiazolidinediones) have also been shown to reduce CRP levels in people with or without diabetes mellitus. This effect was seen independent of their glucose-lowering effects.
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How can you lower your C-reactive protein blood levels?
The overall outlook for those with an elevated CRP largely depends on the cause. In general, the level may be elevated as a response to any inflammation or infection present in the body. The outlook will depend on the success of treatment directed at the underlying cause of the inflammation.
More specifically, as a risk assessment tool for cardiovascular disease, the elevation of CRP correlates with the presence of traditional cardiac risk factors including:
- hypertension (high blood pressure),
- high cholesterol,
- diabetes mellitus,
- obesity,
- advanced age,
- cigarette smoking, and
- strong family history of cardiac disease.
Appropriate medical management of these risk factors include:
- diet,
- exercise, and
- smoking cessation.
Medical treatment and management of the risk factors for elevated C-reactive protein blood levels are important to prevent future cardiovascular disease.
Eating anti-inflammatory foods such as green leafy vegetables, nuts, fatty fish, and whole grains may help lower inflammation leading to high CRP levels. Avoiding inflammatory foods such as refined carbohydrates, fried foods, red meat, and processed meat can also help lower inflammation in the body. Always choose fresh food over processed food to lower inflammation in the body.
How can low, moderate, and elevated C-reactive protein values predict potential heart disease?
According to the American Heart Association (AHA) and the CDC, the following guidelines are recommended for the assessment of cardiovascular risk in regard to high-sensitivity C-reactive protein (hs-CRP) levels:
- Low risk for cardiovascular disease if hs-CRP is 1 milligram (mg) per liter or less
- Moderate risk for cardiovascular disease if hs-CRP is between 1 and 3 mg per liter
- High risk for cardiovascular disease if hs-CRP is greater than 3 mg per liter
CRP level of greater than 10 mg per liter may be seen in an acute plaque rupture, such as a heart attack or stroke, provided there is no other explanation for the elevated level (other inflammatory or infectious process).
The cardiovascular risk in regards to hs-CRP levels chart.
| Risk | hs-CRP Level |
|---|---|
| Low risk | 1 milligram (mg) per liter or less |
| Moderate risk | between 1 and 3 mg per liter |
| High risk | greater than 3 mg per liter |
| Acute plaque rupture (a stroke or heart attack) | greater than 10 mg per liter |
Examining CRP levels through CRP blood tests may help determine the course of treatment for patients with moderate risk.
Are elevated C-reactive protein levels a risk factor for heart disease inflammation?
Because of the inflammatory component of atherosclerosis, it may correlate with an elevated CRP level and has been linked with cardiovascular disease. However, based on the currently available data it cannot be considered an independent risk factor for cardiovascular disease.
The traditional risk factors for cardiovascular disease, include
- high blood pressure (hypertension),
- type 2 diabetes,
- elevated blood cholesterol,
- age,
- cigarette smoking,
- obesity, and
- family history of heart disease.
According to recent studies, after adjusting for these traditional risk factors, elevated CRP level alone is unlikely to be a cause of cardiovascular disease.
Nevertheless, CRP may be used as a predictor of cardiovascular disease based on its correlation with the other known cardiac risk factors and their role in the formation of atherosclerosis. In individuals with some or all of these traditional risk factors, elevated CRP levels have been detected. Some data even suggest a trend of higher CRP elevation in the presence of a higher number of risk factors.
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Is there a link between C-reactive protein and heart attack and stroke risk?
The elevation of CRP has also been linked to atherosclerosis and heart disease. Atherosclerosis, or cholesterol plaquing of the arteries, is known to have an inflammatory component that is thought to cause the rise in CRP levels in the blood. Atherosclerosis is also felt to be affected by age and other cardiovascular risk factors, including diabetes mellitus, high cholesterol, high blood pressure, and cigarette smoking.
In atherosclerosis, the blood vessel wall becomes injured. This injury acts as a focus of inflammation and leads to the formation of plaques in the blood vessel walls. The plaques typically contain blood cells of inflammation, cholesterol deposits, and debris from the injured cells in the blood vessel lining. The accumulation of these elements leads to the narrowing of the wall of the blood vessel. The blood vessel narrowing can hinder the blood flow, and the plaque can rupture and flake off the blood vessel wall, causing blockage and leading to strokes and heart attacks.
The burden of plaques in the body can be proportional to the degree of CRP elevation in persons with atherosclerosis. Atherosclerotic plaques can exist in different stages throughout the body. It is therefore essential to monitor CRP levels in the blood to identify any risk for heart attack and stroke.
Frequently asked questions
- What happens if CRP (C-reactive protein) is high? If C-reactive protein is high, it could indicate inflammation associated with a serious underlying condition.
- How much CRP level is dangerous? CRP levels of more than 50 mg/dL are considered to be severe and dangerous.
- What is the CRP normal range? The CRP normal range may vary from lab to lab. However, the most commonly accepted CRP normal range is less than 0.3 mg/dL, with some labs considering a range between 0.3 and 1 mg/dL as normal.
- What to do if CRP is positive? If CRP is positive, consult your physician to understand your results and ways to lower the CRP levels effectively.
- What foods increase CRP? Foods that cause inflammation are known to increase CRP levels. Some foods that increase CRP levels include red meat, processed foods, fried foods, and refined carbohydrates.
- Should I be worried about high CRP? If you have high CRP levels, it could indicate inflammation associated with serious conditions. You should consult your physician for further management
- What infections cause very high CRP? Infections such as hepatitis C, bacterial sepsis, dengue, and malaria are known to cause very high CRP levels.
From 
Medically Reviewed on 1/15/2025
References
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