What Is CRP in a Blood Test?

Q: What Is CRP in a Blood Test?

CRP (C-Reactive Protein) explained: normal below 3 mg/L, what high CRP means (infection, inflammation, cardiovascular risk), and the difference between standard CRP and hs-CRP.

CRP stands for C-Reactive Protein. Produced by your liver in response to inflammation anywhere in your body. Rises within hours of tissue injury.

Normal Range

Below 3 mg/L — low cardiovascular risk
3–10 mg/L — moderate (chronic inflammation, obesity)
Above 10 mg/L — acute inflammation or infection
Above 100 mg/L — usually acute bacterial infection

Standard CRP vs hs-CRP

Standard CRP: detects acute inflammation and infection
hs-CRP: cardiovascular risk assessment
hs-CRP below 1: low CV risk
hs-CRP 1–3: average risk
hs-CRP above 3: high CV risk

Elevated CRP Causes

Bacterial infection — rises dramatically
Viral infection — rises modestly
Autoimmune disease — RA, lupus, IBD
Obesity
Smoking
Trauma or surgery
Cancer

Clinical Use

Distinguish bacterial from viral infection
Monitor autoimmune disease activity
Assess cardiovascular risk (hs-CRP)
Monitor anti-inflammatory treatment response

Source: NLM MedlinePlus, American Association for Clinical Chemistry.

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