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hs-CRP Blood Test: What It Measures and What Results Mean

What an hs-CRP blood test measures, how it differs from a standard CRP test, how to prepare, and how clinicians read the results in context.

An hs-CRP blood test measures very small amounts of C-reactive protein (CRP) in your blood. CRP is a protein your liver makes in response to inflammation. The "hs" stands for high-sensitivity: this version of the test can pick up smaller increases in CRP than a standard CRP test, and clinicians mainly use it as one piece of a heart disease risk assessment (Mayo Clinic).

This guide explains what CRP is, how the two versions of the test differ, how to prepare, and how results are usually read. It is meant to help you follow the conversation with your clinician, not to replace it.

What is C-reactive protein?

Inflammation is your body's way of protecting tissue and helping it heal from an injury, an infection, or another illness. MedlinePlus describes short-term, or acute, inflammation as helpful. When you get a cut, for example, the area may turn red and swell while your body works to stop infection (MedlinePlus).

When inflammation lasts too long, it can damage healthy tissue. This is called chronic inflammation. MedlinePlus says it is most often caused by certain autoimmune disorders, and it can also happen when tissue is repeatedly irritated, for example by smoking or chemicals in the environment.

Your liver releases CRP into your bloodstream when inflammation is present. You normally have low levels in your blood, and the level rises and falls with the amount of inflammation in your body (Cleveland Clinic).

One important limit: a CRP result can show that inflammation is present, but not what is causing it or where it is in the body. Both MedlinePlus and Cleveland Clinic make this point, which is why CRP is almost always read alongside other tests, symptoms, and your medical history.

hs-CRP blood test vs. standard CRP test

Both tests measure the same protein. The difference is how small a change they can detect, and what clinicians use them for.

Standard CRP test

A standard CRP test is usually ordered to look for or follow larger amounts of inflammation. According to MedlinePlus and Cleveland Clinic, a clinician may order it to:

Check for a bacterial or viral infection, especially with symptoms such as fever, chills, a rapid heart rate, rapid breathing, or nausea and vomiting
Help evaluate chronic inflammatory conditions, such as rheumatoid arthritis, lupus, vasculitis, or inflammatory bowel disease
Watch for infection after surgery
Follow how an infection or chronic inflammatory condition is responding to care

Because CRP goes up and down with inflammation, a falling CRP level over time can be a sign that inflammation is easing (MedlinePlus).

High-sensitivity CRP test

MedlinePlus notes that people sometimes confuse the two tests. An hs-CRP test measures very tiny increases in CRP, and it is used to estimate the risk of heart disease (MedlinePlus).

Mayo Clinic explains that a high hs-CRP level has been linked to an increased risk of heart attacks, and that people who have already had a heart attack are more likely to have another if their hs-CRP level is high. The hs-CRP test can help show the risk of coronary artery disease, a condition in which the blood vessels of the heart narrow (Mayo Clinic).

Who might get an hs-CRP test?

Mayo Clinic is direct that an hs-CRP test isn't for everyone. Since the test doesn't show the cause of inflammation, it's possible to have a high hs-CRP level that has nothing to do with the heart.

According to Mayo Clinic, the test may be most useful for people who have a 10% to 20% chance of having a heart attack within the next 10 years, which is called intermediate risk. A healthcare professional estimates that risk by looking at things like lifestyle, family history, and overall health (Mayo Clinic).

In other words, hs-CRP is usually an add-on to a broader heart health review, not a stand-alone screening test. Your clinician decides whether it adds anything useful in your situation.

How to prepare for an hs-CRP blood test

Your clinician will tell you exactly how to prepare. A few points from the sources are worth knowing ahead of time:

Skip hard exercise beforehand if asked. Mayo Clinic says your care team might ask you to avoid intense activity, such as heavy weight training or a long run, before the test, because it can cause a sudden jump in CRP.
List your medicines and supplements. Some medicines can affect CRP. MedlinePlus specifically mentions magnesium and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin. Don't stop any prescription medicine without talking with your clinician first.
Fasting depends on the other tests. Cleveland Clinic says most people don't need to do anything special, such as fasting, for a CRP test. Mayo Clinic notes that if your blood will also be used for other tests, you may be asked not to eat or drink for a while. An hs-CRP test for heart risk is often drawn at the same time as a cholesterol test.

The draw itself is a standard blood sample from a vein in your arm and usually takes less than five minutes. There is very little risk. You may have brief soreness or a small bruise where the needle went in (MedlinePlus).

What hs-CRP results mean

Reference ranges vary from lab to lab, and your report will show the range the lab used. Your clinician interprets your result using your health history and other test results.

A note on units

CRP results can be reported in two units, which can make two reports look very different:

Milligrams per liter (mg/L), which Mayo Clinic uses
Milligrams per deciliter (mg/dL), which MedlinePlus and Cleveland Clinic use for standard CRP

A deciliter is one-tenth of a liter, so a number in mg/dL is one-tenth of the same amount written in mg/L. Check the unit on your report before comparing numbers.

hs-CRP results and heart disease risk

Mayo Clinic says hs-CRP results are usually given as follows:

Lower risk of heart disease: less than 2.0 mg/L
Higher risk of heart disease: 2.0 mg/L or greater

CRP levels change over time. Mayo Clinic notes that a coronary artery disease risk assessment is usually based on the average of two hs-CRP tests, ideally taken two weeks apart (Mayo Clinic).

Just as important, Mayo Clinic says hs-CRP is only one risk factor for coronary artery disease, and a high level doesn't always mean a higher risk of developing heart disease. Other results help fill in the picture.

Standard CRP results

For a standard CRP test, MedlinePlus describes a value of 0.8 to 1.0 mg/dL or lower as a healthy amount, and Cleveland Clinic gives a general normal level of less than 0.9 mg/dL. Mayo Clinic, which reports in mg/L, says results of 8 or 10 mg/L or higher are considered high. A high result is a sign of inflammation that may come from infection, injury, or chronic disease, and your clinician may order more tests to find the cause.

Things that can nudge CRP up

A modestly raised CRP does not always point to a serious problem. The sources list several everyday factors linked to higher CRP, including:

Smoking
A recent cold or a recent injury
Gum disease, such as gingivitis or periodontitis
Obesity or diabetes
Insomnia or depression
Pregnancy
Hormone therapy for menopause

MedlinePlus and Cleveland Clinic also note that females tend to have slightly higher CRP levels than males, and Cleveland Clinic adds that older adults do too.

Cleveland Clinic also points out that an elevated result doesn't necessarily mean you have a condition that needs treatment, and that roughly 1 in 20 healthy people will have results outside the normal range. Errors in collecting, transporting, or processing a sample can also affect a result (Cleveland Clinic).

How hs-CRP fits with your other labs

Because hs-CRP is a heart risk marker, it is read as one part of a broader heart health picture, and Mayo Clinic notes it is often drawn at the same time as a cholesterol test. If you are reviewing other lab work, our guides to the fasting insulin test and the hormone panel test explain how those numbers are read in context as well.

When to talk to a clinician

Consider asking a licensed clinician about CRP or hs-CRP testing if:

You want a fuller picture of your heart health and have risk factors such as a family history of heart disease
A past CRP or hs-CRP result came back high and you want to understand what it means or whether to repeat it
You have a chronic inflammatory condition and want to know how your labs are being followed
You take hormone therapy, NSAIDs, or supplements and want to know whether they could affect your results

Some symptoms should not wait for lab work. Fever with chills, a rapid heart rate, and rapid breathing can be signs of a serious infection, and MedlinePlus describes sepsis as a life-threatening medical emergency. Chest pain or other signs of a heart attack also need emergency care. Call 911 or seek urgent care right away.

If you are exploring telehealth, Age Edit coordinates access to lab testing through independent licensed providers in our partner network, available in all 50 states. The treating clinician reviews your history, decides which tests make sense for you, explains the results, and makes all clinical decisions. You can start at /get-started.

Sources

This article is for general education and is not medical advice. A licensed clinician in your state decides whether any test or treatment is right for you.

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