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C-Reactive Protein (CRP) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

C-Reactive Protein (CRP) Test

A C-reactive protein (CRP) test measures the level of CRP in your blood to help your healthcare provider identify and monitor inflammation in your body.

What is a C-reactive (CRP) protein test?

A C-reactive protein test measures the level of c-reactive protein (CRP) in a sample of your blood. Your liver makes CRP in response to inflammation.

Inflammation is your body's way of protecting your tissues and helping them heal from an injury, infection, or other disease. When it's acute (sudden) and for a short time, inflammation is helpful. For example, when you get a cut on your skin, the area around the cut may turn red and swell. These are signs that inflammation is working to stop infection. Inflammation acts in a similar way when responding to germs or harmful substances (toxins) inside your body.

If inflammation lasts too long, however, it can damage healthy tissues. This is called chronic (long-term) inflammation, and it is most often caused by certain autoimmune disorders. Chronic inflammation can also happen if your tissues are repeatedly injured or irritated, for example from smoking or chemicals in the environment.

What is it used for?

By measuring the levels of c-reactive protein in your blood, a CRP test can tell your health care provider how much inflammation you have in your body. High CRP levels may mean you have an acute or chronic health condition, such as:

  • Infections from bacteria or viruses.
  • Inflammatory bowel disease, disorders of the intestines that include Crohn's disease and ulcerative colitis.
  • Autoimmune disorders, such as lupus, rheumatoid arthritis, and vasculitis.
  • Lung diseases, such as asthma.

Smoking and exposure to environmental toxins such as polluted air and hazardous waste can also cause high CRP levels.

Why do I need a CRP test?

You may need this test if you have symptoms of a bacterial infection, such as:

  • Fever or chills
  • Rapid heart rate
  • Rapid breathing
  • Nausea and vomiting

You may also need a CRP test if your provider wants to:

  • Check for a chronic condition that causes inflammation.
  • Monitor for infection after surgery.
  • Monitor your condition and treatment if you have an infection or a chronic condition.
  • Make treatment decisions if you have sepsis. Sepsis is your body's extreme response to an infection that spreads to your blood. It's a life-threatening medical emergency.

CRP levels rise and fall depending on how much inflammation is in your body. So, if your CRP levels fall, it's a sign that your treatment for inflammation is working or that you're healing on your own.

What happens during a CRP test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This process usually takes less than five minutes.

Will I need to do anything to prepare for the test?

Some medicines may affect your results. So, tell your provider about any supplements or medicines that you take, including magnesium and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen and aspirin. Don't stop taking any prescription medicines without talking with your provider first.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

In general, healthy people have very low amounts of CRP in their blood. A value of 0.8-1.0 milligrams per deciliter (mg/dL) or lower is thought to be a healthy amount. Any increases above normal may mean you have inflammation in your body. However, increases can also be linked to:

  • Insomnia.
  • Depression.
  • Hormone replacement therapy.
  • Obesity.
  • Sex. Females often have slightly higher CRP levels than males.

Your CRP test results tell you how much inflammation you have in your body, but not what's causing it or where it is. To make a diagnosis, your provider will look at your CRP results along with the results of other tests, your symptoms, and medical history.

Is there anything else I need to know about a CRP test?

A CRP test is sometimes confused with a high-sensitivity (hs) CRP test. They both measure CRP, but they are used for different conditions. An hs-CRP test measures very tiny increases in your CRP levels. It is used to estimate your risk of heart disease.

Frequently Asked Questions

standard CRP test is used to detect significant inflammation caused by acute infections, injuries, or active autoimmune flares, and it measures higher levels of the protein. A high-sensitivity CRP (hs-CRP) test is designed to detect very low levels of CRP in the blood and is primarily used to assess long-term cardiovascular risk. If your standard CRP is elevated, it usually indicates an active health issue that needs immediate attention, whereas a mildly elevated hs-CRP suggests a chronic, low-grade inflammation that may increase the risk of heart disease over time. Can lifestyle factors like diet or stress cause my CRP levels to be temporarily elevated?::Yes, several lifestyle factors can influence CRP levels. Poor sleep, high levels of psychological stress, and a diet high in processed foods and saturated fats can contribute to chronic low-grade inflammation, potentially raising your CRP. Additionally, recent intense exercise or a minor, unnoticed infection can cause a temporary spike. For the most accurate baseline, especially for cardiovascular risk assessment, it is recommended to avoid strenuous exercise for 24 hours before the test and to ensure you are not currently fighting off a cold or flu. How do I interpret a CRP result that is slightly above the normal range?::A slightly elevated CRP (for example, between 1.0 and 3.0 mg/L on a standard scale) is often non-specific and may not point to a single serious disease. It could indicate mild inflammation from a recent minor injury, a resolving infection, or early signs of an autoimmune condition. Your healthcare provider will interpret this result in the context of your symptoms and other blood tests. If you have no symptoms, your doctor may recommend repeating the test in a few weeks to see if the level normalizes or if it trends upward, which would warrant further investigation. Does taking anti-inflammatory medications like ibuprofen or aspirin affect the accuracy of a CRP test?::Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen can lower CRP levels because they reduce inflammation. If you are taking these medications regularly, it is important to inform your doctor, as they may ask you to pause them for a short period before the test to get a true baseline of your inflammatory status. However, you should never stop taking prescribed medications without consulting your healthcare provider first, as the risks of stopping certain drugs may outweigh the benefit of a slightly more accurate CRP reading.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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