C-Reactive Protein Test: Purpose, Procedure, and Results (2024)

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A doctor may order a C-reaction protein test if they suspect you have an inflammatory disorder, such as arthritis. Your doctor may also use this test to monitor treatment if you’ve been diagnosed with an inflammatory disorder.

C-reactive protein (CRP) is a substance the liver produces in response to inflammation.

A high level of CRP in the blood can be a marker of inflammation. A wide variety of conditions can cause it, from an infection to cancer.

High CRP levels can also indicate that there’s inflammation in the arteries of the heart, which can mean a higher risk of heart attack.

However, the CRP test is an extremely nonspecific test. CRP levels can be elevated in many inflammatory conditions.

If your doctor suspects you may have an inflammatory disorder (like arthritis, cancer, an infection, etc.), they may order a C-reaction protein test. This test can show there’s a high level of inflammation, but it does not show where the inflammation is located or what might be causing it.

If you have a previously diagnosed inflammatory issue, your doctor may also order this test occasionally to see how your treatment is working, and if the issue is being properly managed.

It’s important to note that ahigh-sensitivity C-reactive protein (hs-CRP) test is a slightly different test than a regular C-reaction protein test. This test typically predicts heart disease and stroke.

While the regular C-reactive test can help uncover different diseases that cause inflammation by measuring high levels of protein, the hs-CRP test measures lower (but still elevated) levels of protein, which can signal the risk of heart disease and stroke.

Your doctor may order a hs-CRP if they’re focusing on cardiovascular issues.

CRP and heart disease

Expert opinion from the American Heart Association in 2019 states that when considering all risk factors, people with CRP levels greater than or equal to 2 milligrams per liter (mg/L) may need more intense measures to prevent cardiovascular disease.

Elevated levels of CRP may have an important role in identifying people who might need closer follow-up or more intensive treatment after heart attacks or heart procedures.

CRP levels may also be useful in identifying people at risk of heart disease when cholesterol levels alone may not be helpful.

The Centers for Disease Control and Prevention (CDC) considers the following as significant risk factors for developing heart disease:

  • diabetes
  • high blood pressure
  • high cholesterol
  • smoking
  • a diet low in nutrients and higher in fat and refined carbs
  • physical inactivity
  • heavy alcohol use
  • overweight and obesity

A family history of heart disease can also put you at a higher risk of heart disease.

No special preparation is necessary for this test. You may eat normally on the day of, and the test can happen at any time of day.

This test is done via a blood sample, so there will be a small needle involved.

A nurse or other healthcare professional will draw blood from a vein, usually on the inside of your elbow or the back of your hand.

First, they clean the skin over the vein with antiseptic. Next, they wrap an elastic band around your arm, causing your veins to bulge out slightly. The healthcare professional then inserts a small needle into the vein and collects your blood in a sterile vial.

After the healthcare professional collects your blood sample, they remove the elastic band around your arm and ask you to apply pressure to the puncture site with gauze. They may use tape or a bandage to hold the gauze in place.

Are there risks with the test?

There are no risks associated with this test other than routine issues that can occur with any blood test. The main issues include:

  • a slight pinch when the needle is inserted
  • slight bruising at needle insertion site

If you’re nervous around needles or blood, talk with the healthcare professional administering the test about ways to make it more comfortable for you.

In general, the results of your test will be measured in either mg/dL or mg/L.

Your doctor will most likely explain the results of your test to you, but in general:

  • A typical result: Less than 10 mg/L
  • A high result: Equal to or greater than 10 mg/L

According to a 2003 study by the American Heart Association, people with a higher level of CRP were two to three times more likely to have a heart attack than people with lower levels of CRP.

A small study from 2013 evaluated 100 people with cardiovascular risk factors. Researchers found that a CRP level over 10 mg/L was connected to a 4 percent risk of developing a fatal cardiovascular disease in 10 years.

If your doctor believes you may be at risk of heart disease or stroke, they may order a hs-CRP blood test alongside other tests.

Additionally, there’s more recent research that suggests CRP may be used as a predictor of health outcomes related to chronic obstructive pulmonary disease (COPD).

If your doctor is concerned you are dealing with the symptoms of other inflammatory conditions besides cardiovascular issues, they may order a regular CRP test to diagnose, among other things:

  • inflammatory bowel disease (IBD)
  • rheumatoid arthritis
  • lupus

Lowering your CRP isn’t a guaranteed way to lower your risk of cardiovascular or autoimmune disease.

It’s important to know that high CRP is what doctors call a biomarker. A biomarker is a factor to keep in mind when analyzing a person’s health, but not a stand-alone indicator of a particular diagnosis.

A 2015 study indicates that eating a nutritious, balanced diet — including lots of fruits, vegetables, and fiber — may help lower your CRP concentration.

If you’re at high risk of cardiovascular disease and your test results show high CRP, your doctor may suggest a statin or other cholesterol-lowering medication.

Vitamin C has also been explored as a way to lower CRP levels for people who have an elevated risk of cardiovascular disease.

A 2017 research review suggests that probiotics may also have a positive effect in lowering CRP.

However, more studies have to be done for each method before any definitive claims can be made.

C-reactive protein (CRP) is a substance the liver produces in response to inflammation.

If your doctor suspects you may have a high level of inflammation, they may order a CRP blood test as one way to identify the underlying cause of that inflammation.

While a CRP blood test can’t say what exactly is causing your inflammation, your doctor may be able to use it to help them diagnose your issue.

Sometimes a high CRP measurement can be a risk factor for cardiovascular disease.

If you’ve recently noticed changes in your body that aren’t going away and causing you discomfort, talk with your doctor about your symptoms. A CRP blood test may be one of the tests your doctor decides to order.

C-Reactive Protein Test: Purpose, Procedure, and Results (2024)


What is the purpose of C reactive protein test? ›

What is this test? The C-reactive protein (CRP) test is used to find inflammation in your body. Inflammation could be caused by different types of conditions, such as an infection or autoimmune disorders like rheumatoid arthritis or inflammatory bowel disease. This test measures the amount of CRP in your blood.

How do you interpret C reactive protein results? ›

You are at low risk of developing cardiovascular disease if your hs-CRP level is lower than 1.0 mg/L. You are at average risk of developing cardiovascular disease if your levels are between 1.0 mg/L and 3.0 mg/L. You are at high risk for cardiovascular disease if your hs-CRP level is higher than 3.0 mg/L.

What is an alarming CRP? ›

A CRP test result of more than 50 mg/dL is generally considered severe elevation. Results over 50 mg/L are associated with acute bacterial infections about 90% of the time.

What should I do if my C reactive protein is positive? ›

If you're at high risk of cardiovascular disease and your test results show high CRP, your doctor may suggest a statin or other cholesterol-lowering medication. Vitamin C has also been explored as a way to lower CRP levels for people who have an elevated risk of cardiovascular disease.

What will happen if C-reactive protein is high? ›

A high level of hs-CRP in the blood has been linked to an increased risk of heart attacks. Also, people who have had a heart attack are more likely to have another heart attack if they have a high hs-CRP level. But their risk goes down when their hs-CRP level is in the typical range. An hs-CRP test isn't for everyone.

What is C-reactive protein indicated for? ›

CRP is a useful indicator to assess and monitor the presence, severity, and course of the inflammatory response in infectious and noninfectious disorders including acute myocardial infarction, angina, malignancies, rheumatoid arthritis, inflammatory bowel disease, burns, trauma, and after surgical procedures.

What kind of inflammation 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 cancers cause high CRP? ›

Additionally, elevated CRP levels are associated with poor survival in many malignant tumors, such as soft tissue sarcoma, prostate cancer, breast cancer, renal cell carcinoma, colorectal cancer, non-small-cell lung cancer, malignant lymphoma, and pancreatic cancer (10, 13-20).

What is a good range for C-reactive protein? ›

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).

What is a bad CRP number? ›

hs-CRP level lower than 1.0 milligrams per liter (mg/L) – low risk of CVD (heart disease) hs-CRP level of 1.0 mg/L to 3.0 mg/L – moderate risk of CVD. hs-CRP level of more than 3.0 mg/L – high risk of CVD.

When should I worry about CRP? ›

Typically, CRP levels are low or undetectable in healthy individuals. A normal range falls between 0 to 3 milligrams per liter (mg/L) of blood. Elevated levels may signal an underlying health concern. While there is no such thing as a “low” CRP level, the normal range is generally less than 0.9 mg/dL.

What CRP level needs antibiotics? ›

The normal serum concentration of CRP is usually <10 mg/L but, in severe bacterial infections, it can rise as high as 500 mg/L.5 In the literature, various cut-off points have been proposed to distinguish between viral and bacterial infections, but there appears to be a consensus that a CRP value of <40 mg/L is ...

What medicine to take if CRP is high? ›

Angiotensin receptor blockers (ARBs) (valsartan, irbesartan, olmesartan, telmisartan) markedly reduce serum levels of CRP. The findings with other ARBs (losartan and candesartan) were inconsistent. Antidiabetic agents (rosiglitazone and pioglitazone) reduce CRP levels, while insulin is ineffective.

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

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.

Why am I being tested for C-reactive protein? ›

The C-reactive protein (CRP) blood test checks for inflammation in your body. A CRP blood test will show if there is inflammation in your body. A CRP blood test also helps to see how well you are responding to treatment. No special preparation is needed for a CRP blood test.

What is the most common cause of high CRP? ›

Significantly elevated CRP levels tend to occur with severe infections, such as bacterial or fungal infections. Bacterial infection is responsible for about 90% of the cases involving CRP levels higher than 50 mg/l.

What is the clinical significance of a positive C-reactive protein test? ›

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.

What happens if C-reactive protein is low? ›

You are at low risk of developing cardiovascular disease if your hs-CRP level is lower than 1.0 mg/L. You are at average risk of developing cardiovascular disease if your levels are between 1.0 mg/L and 3.0 mg/L. You are at high risk for cardiovascular disease if your hs-CRP level is higher than 3.0 mg/L.

How long does it take for CRP to return to normal after an infection? ›

The serum CRP level in a “healthy” person is usually less than 5 mg/L; this will begin to rise four to eight hours after tissue is damaged, peak within 24 – 72 hours, and return to normal two to three days after the pathological process has ceased.

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