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

The C-reactive protein (CRP) test is a blood test that checks for inflammation in your body.

CRP is a protein that is made in your liver and released into your bloodstream. When your body has inflammation, infection or tissue damage, CRP levels rise quickly, often within 24 to 48 hours.

• Inflammation is your body's natural way of fighting off infections, injuries or irritations. It can cause redness, swelling and pain.
• Infection happens when germs, such as bacteria or viruses, enter your body and make you sick.
• Tissue damage is when cells or tissues in your body are hurt by an injury, illness or disease.

The CRP blood test can be used to find out how severe the inflammation is or if treatment is working. It does not show where the inflammation is in your body, or what caused it.

When is a CRP blood test used?

Your doctor may suggest this test if they suspect you have:

• an infection
• an illness related to inflammation, such as rheumatoid arthritis, lupus or inflammatory bowel disease (Crohn's disease or ulcerative colitis)
• an infection after your waters break early during pregnancy

A CRP test can help detect inflammation in your body, and assess how well you are responding to treatment.

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C-reactive protein high sensitivity (hsCRP)

A more sensitive form of the test, called high-sensitivity CRP (hsCRP), may help assess your risk of heart disease. This is used in combination with your other risk factors.

Where can I get a CRP blood test?

You usually need to go to a pathology collection centre. Your doctor will recommend one near you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

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How do I prepare for a CRP blood test?

There is no special preparation needed for a CRP blood test.

However, if you are having other blood tests done at the same time, there may be special instructions you need to follow.

Check with your doctor or the pathology collection centre when you get your referral. Ask them if there is anything you need to do before your blood test.

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What happens during a CRP blood test?

A blood test is usually done at a pathology collection centre. A health professional will take a sample of blood, usually from a vein in your arm. The blood will then be sent to a laboratory for testing.

What do my CRP blood test results mean?

An elevated CRP is more than 10mg/L. This means there is inflammation somewhere in your body. Other tests may be necessary to find out where the inflammation is or what is causing it. As CRP is a very non-specific measure, it is important that you seek medical advice and not try to interpret the number on your own.

If you are being treated for an infection or inflammation, your CRP levels should decrease.

A normal CRP is less than 5mg/L.

You should always discuss your blood test results with your doctor to understand what they mean for you.

Your doctor will look at your blood test results in the context of your situation and the reasons you are having the test. CRP levels can be influenced by factors, such as your:

• age
• sex
• smoking status
• medical treatments
• health conditions

Resources and support

Pathology Tests Explained has more information about C-reactive protein.

Read our 'Guide to blood testing' to learn more about blood tests, including:

• what to consider before having the test
• what happens during a blood test
• how accurate results are
• blood test costs

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.