C-reactive protein (CRP) test: what it means

By the pharmaranks editorial teamReviewed against MedlinePlus (U.S. National Library of Medicine) sourcesUpdated Jul 3, 2026How we research

What it measures

A C-reactive protein (CRP) test measures the level of C-reactive protein in a sample of your blood. CRP is a protein your liver makes in response to inflammation, so its level tends to rise when inflammation is present in the body. A CRP result tells you how much inflammation there may be, but not what is causing it or where it is located. (A separate, more sensitive version called high-sensitivity CRP, or hs-CRP, is a different test used to help estimate heart disease risk.)

Why it’s ordered

A clinician may order a CRP test as a general way to check for inflammation in the body. It is commonly used to help look for a condition that causes inflammation, to help monitor for infection (for example, after surgery), and to help track how well treatment is working over time. It is interpreted alongside your symptoms, exam, and other tests, not on its own.

General reference range

As a general reference, MedlinePlus notes that most healthy adults have CRP levels less than about 0.3 mg/dL, and that a value around 0.8-1.0 mg/dL or lower is often considered a healthy amount. These are general figures only. Normal CRP values vary from one laboratory to another, and levels often rise slightly with age and can differ by sex, so the reference range printed on your own lab report is what applies to your result. A number by itself is not a diagnosis, and results vary by lab, age, and sex.

If it’s high

A higher-than-expected CRP level suggests that inflammation may be present somewhere in the body, but it does not identify the cause. As general, non-exhaustive examples, a raised CRP can be seen with infections from bacteria or viruses; inflammatory bowel disease such as Crohn's disease or ulcerative colitis; and autoimmune conditions such as lupus, rheumatoid arthritis, or vasculitis. Markedly high levels (for example, above about 10 mg/dL) may be associated with things such as a significant infection or an inflammatory or autoimmune flare, among other conditions. These are possible associations only, not a diagnosis, and only a clinician can determine what an elevated result means for you.

If it’s low

CRP is generally not reported as being abnormally "low," and a low value is not treated as a problem — healthy people usually have very low amounts of CRP in their blood. Importantly, a low or normal CRP does not always mean there is no inflammation present. Some conditions, including rheumatoid arthritis and lupus, may not raise CRP even when disease is active. In someone being treated, a falling CRP over time can be a general sign that inflammation is settling, but this should be interpreted by a clinician in context.

A result is not a diagnosis

Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.

Frequently asked

What does the C-reactive protein (CRP) test test measure?: A C-reactive protein (CRP) test measures the level of C-reactive protein in a sample of your blood. CRP is a protein your liver makes in response to inflammation, so its level tends to rise when inflammation is present in the body. A CRP result tells you how much inflammation there may be, but not what is causing it or where it is located. (A separate, more sensitive version called high-sensitivity CRP, or hs-CRP, is a different test used to help estimate heart disease risk.)
What is a normal C-reactive protein (CRP) test range?: As a general reference, MedlinePlus notes that most healthy adults have CRP levels less than about 0.3 mg/dL, and that a value around 0.8-1.0 mg/dL or lower is often considered a healthy amount. These are general figures only. Normal CRP values vary from one laboratory to another, and levels often rise slightly with age and can differ by sex, so the reference range printed on your own lab report is what applies to your result. A number by itself is not a diagnosis, and results vary by lab, age, and sex.
What does a high result mean?: A higher-than-expected CRP level suggests that inflammation may be present somewhere in the body, but it does not identify the cause. As general, non-exhaustive examples, a raised CRP can be seen with infections from bacteria or viruses; inflammatory bowel disease such as Crohn's disease or ulcerative colitis; and autoimmune conditions such as lupus, rheumatoid arthritis, or vasculitis. Markedly high levels (for example, above about 10 mg/dL) may be associated with things such as a significant infection or an inflammatory or autoimmune flare, among other conditions. These are possible associations only, not a diagnosis, and only a clinician can determine what an elevated result means for you.
What does a low result mean?: CRP is generally not reported as being abnormally "low," and a low value is not treated as a problem — healthy people usually have very low amounts of CRP in their blood. Importantly, a low or normal CRP does not always mean there is no inflammation present. Some conditions, including rheumatoid arthritis and lupus, may not raise CRP even when disease is active. In someone being treated, a falling CRP over time can be a general sign that inflammation is settling, but this should be interpreted by a clinician in context.

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Sources

General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.