What Is CRP (C-Reactive Protein)?

Inflammation is the body's natural response to injury, infection, or irritation, and it produces measurable signals in the blood. C-reactive protein is one of those signals. Made by the liver, CRP tends to rise when inflammation is present and settle again as it resolves, which makes it a useful general indicator of inflammatory activity.

CRP is not tied to one place in the body. It reflects inflammation broadly, wherever it may be occurring, rather than pointing to a specific organ or cause. That broad nature is both its strength — it can flag that something is stirring — and its limitation, since it does not, on its own, say where or why.

Clinicians may order CRP when they want a general sense of whether inflammation is present and how it is changing. Because CRP responds to a wide range of inflammatory processes, it can serve as a broad marker that a clinician weighs alongside symptoms, an exam, and other tests.

It is sometimes followed over time, since watching CRP rise or settle can add context to a larger clinical picture. As with any single marker, a clinician decides when CRP is worth measuring and reads it as one input rather than a stand-alone answer to any particular question.

There are two common ways to measure the same protein. Standard CRP is used to gauge more noticeable inflammation, the kind associated with a broad range of inflammatory activity. A high-sensitivity version, called hs-CRP, is designed to detect smaller, more subtle amounts of the protein.

That added sensitivity is why hs-CRP is often discussed in a cardiovascular risk context, where low-grade inflammation is one of the threads clinicians consider for heart health. The substance being measured is the same; the difference lies in how finely the test reads it and the setting in which a clinician chooses one version or the other.

CRP is associated with the general level of inflammation in the body. Clinicians describe patterns in which CRP tends to run higher or lower, and these patterns are linked to how actively the body is mounting an inflammatory response rather than to any single cause.

Because inflammation is broad, many everyday events can move CRP — a recent infection, injury, illness, or other inflammatory condition can all raise it temporarily. That is why timing matters, and why a clinician reads CRP as one thread in a larger story rather than a stand-alone verdict, often interpreting it alongside a person's history and other markers.

CRP is measured with a routine blood draw, typically collected at a patient service center and sent to a laboratory. A clinician may suggest timing the test thoughtfully, since a current illness or injury can temporarily raise the reading and cloud the picture.

Once results return, a clinician interprets them in the context of symptoms, health history, and any other markers ordered. The result belongs inside that conversation, where a clinician can assemble the full picture and decide what, if anything, is worth exploring next.