C-reactive protein (CRP and hs-CRP): what your result means

CRP is an acute-phase protein made mainly by the liver. Its concentration can rise quickly as part of the body's response to inflammation and can fall as that response settles.^{See reference 3,See reference 8}

The test is deliberately nonspecific. It can support a clinician's assessment or help follow a known inflammatory process, but it cannot locate inflammation or distinguish one disease from another. A low result also does not rule out every infection, inflammatory disorder or important illness.^{See reference 3,See reference 4,See reference 5}

CRP is commonly reported in mg/L, while some laboratories use mg/dL. The exact conversion is 1 mg/dL = 10 mg/L and 1 mg/L = 0.1 mg/dL. This changes only the unit; it does not convert standard CRP into hs-CRP.^{See reference 1,See reference 8}

For standard CRP, use the range printed on the report. A representative adult laboratory upper limit may be below 5 mg/L, while other authoritative laboratories use a higher boundary. These are laboratory reference intervals, not universal disease cutoffs or personal targets.^{See reference 4,See reference 5}

A genuine result in nmol/L needs the laboratory's own interpretation. Molar conversion depends on the molecular basis used for CRP, so this guide does not convert nmol/L or apply mass-based mg/L thresholds to it.^{See reference 9,See reference 10}

A standard CRP result above the laboratory range supports the presence of an inflammatory response when the rest of the clinical picture fits. Possible contexts include infection, tissue injury, surgery and inflammatory conditions, but the size of the number alone cannot identify which one applies.^{See reference 3,See reference 4}

A result within the laboratory range can be reassuring for the question being assessed, but it cannot overrule symptoms, examination findings or other tests. Some inflammatory conditions produce only a small CRP response.^{See reference 4,See reference 5}

Repeat testing depends on why CRP was ordered and whether a new result would change care. A fixed schedule is not appropriate for every result.^{See reference 4}

hs-CRP is one risk signal, not a heart-disease test by itself. It should be interpreted with age, blood pressure, smoking, diabetes, cholesterol-related biomarkers, health history and the risk framework used by the clinician.^{See reference 6,See reference 7,See reference 11,See reference 12}

Current U.S. guidance treats hs-CRP at or above 2 mg/L on successive occasions, without another identifiable cause, as a risk-enhancing factor in a defined borderline-risk pathway. European and Canadian guidance also use a value around 2 mg/L selectively, while Australian and UK pathways do not recommend the same routine role. These are decision frameworks, not diagnoses or universal optimal targets.^{See reference 6,See reference 11,See reference 12,See reference 13,See reference 14}

Older categories below 1, from 1 to 3 and above 3 mg/L describe relative population-risk strata. They remain widely repeated online, but they should not replace current clinical guidance or be used as personal treatment targets.^{See reference 15}

For an inflammation question, clinicians may consider symptoms, the trend in CRP and context-specific tests such as a full blood count or erythrocyte sedimentation rate (ESR). A normal ESR or white blood cell count does not automatically cancel an abnormal CRP, because the markers respond differently and answer different questions.^{See reference 4}

For cardiovascular assessment, hs-CRP may sit alongside blood pressure, ApoB or LDL cholesterol, non-HDL cholesterol, triglycerides, lipoprotein(a), diabetes status and smoking history. No fixed combination diagnoses cardiovascular disease, and the appropriate calculator or guideline differs by region.^{See reference 6,See reference 11,See reference 12,See reference 13,See reference 14}

With a high standard CRP, the goal is to understand and manage the underlying cause, not to treat the laboratory number in isolation. Do not self-start antibiotics, anti-inflammatory medicines or supplements based only on CRP.^{See reference 3,See reference 4}

Regular physical activity, a Mediterranean- or DASH-style eating pattern, not smoking and weight management when relevant support overall cardiovascular health. Their value is broader than producing a lower hs-CRP number, and an individual change cannot be promised.^{See reference 7}

Medicines such as statins or anti-inflammatory treatments belong to specific clinician-managed risk or disease pathways. A fall in CRP alone is not proof that a treatment is appropriate or that health outcomes improved. No supplement is established as a treatment for an isolated high CRP result.^{See reference 6,See reference 7,See reference 17}