CRP Blood Test: What It Measures, Uses & What to Expect

C-reactive protein (CRP) is an acute-phase protein synthesized by the liver in response to inflammation (IL-6 driven).

Clinical Uses

• Inflammation marker – infection, autoimmune flares, tissue injury.
• Cardiovascular risk – hs-CRP (<1 mg/L low, 1–3 moderate, >3 high risk).
• Monitor therapy response – RA, vasculitis, IBD, post-op.
• Differentiate – bacterial vs. viral (CRP higher in bacterial); but not specific.

Interpretation

• <10 mg/L: low-grade inflammation / cardiac risk stratification (hs-CRP)
• 10–100 mg/L: moderate inflammation (infection, flare)
• >100 mg/L: severe inflammation (sepsis, major trauma, severe flare)

CRP is non-specific; always correlate with clinical picture, ESR, procalcitonin, imaging.