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Biomarker library / Inflammation

High-sensitivity C-reactive protein (hs-CRP)

Also called cardiac CRP, CRP high sensitivity

C-reactive protein is a liver protein that rises with inflammation. The high-sensitivity assay measures the low concentrations relevant to long-term cardiovascular risk, rather than the large spikes of infection or injury.

Written by the VitalDecades editorial team Reviewed by the editorial review process Updated

01  /  Reference ranges

What counts as normal

Scale in mg/L. Cut points from the sources listed below.
Population Adults without known CVD (CDC/AHA 2003)
Category Low relative risk
Range under 1 mg/L
Source CDC/AHA Statement: Markers of Inflammation and Cardiovascular Disease (2003)

Effective

Population Adults without known CVD (CDC/AHA 2003)
Category Average relative risk
Range 1 to 3 mg/L
Source CDC/AHA Statement: Markers of Inflammation and Cardiovascular Disease (2003)

Effective

Population Adults without known CVD (CDC/AHA 2003)
Category High relative risk
Range over 3 mg/L Values above 10 mg/L should be repeated after ruling out infection or inflammation.
Source CDC/AHA Statement: Markers of Inflammation and Cardiovascular Disease (2003)

Effective

Population Adults, primary prevention (2018 AHA/ACC)
Category Risk-enhancing factor
Range 2 or higher mg/L
Source 2018 AHA/ACC Multisociety Guideline on the Management of Blood Cholesterol

Effective

Normal vs optimal

The categories are relative-risk tertiles, not a disease cutoff. Under 1.0 mg/L is the low-risk tertile. A single elevated value is not meaningful on its own: acute illness, injury, and even a hard workout can raise CRP for days.

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02  /  Why it matters

What the number tells you

The 2003 CDC/AHA statement set the categories still in use for adults without known cardiovascular disease: low risk under 1.0 mg/L, average 1.0 to 3.0, high above 3.0, corresponding to approximate population tertiles, with the high tertile carrying roughly twice the relative risk of the low. It advised averaging two measurements about two weeks apart and discarding any value above 10 mg/L (look for an infection or inflammatory cause, then repeat). The 2018 AHA/ACC cholesterol guideline lists hs-CRP of 2.0 mg/L or higher as a risk-enhancing factor in the statin discussion.

03  /  In practice

Testing and what moves it

When it is tested

  • As an add-on when cardiovascular risk is intermediate and the result would change the decision to treat.
  • Two measurements, fasting or nonfasting, ideally two weeks apart, averaged (CDC/AHA 2003).

What raises it

  • Acute infection or injury (values above 10 mg/L), obesity and insulin resistance, smoking, chronic inflammatory disease, poor sleep, some medications (estrogen).

What lowers it

  • Weight loss, exercise, stopping smoking, statins (which lower hs-CRP independently of LDL-C).

04  /  Related

Read next

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Frequently asked questions

What is a normal hs-CRP? ▼

The CDC/AHA categories are under 1.0 mg/L low, 1.0 to 3.0 average, above 3.0 high relative risk for adults without known heart disease. Values above 10 mg/L usually mean something acute and should be repeated.

Is hs-CRP the same as CRP? ▼

Same protein, different assay range. Standard CRP is used to track infection and inflammatory disease at higher concentrations; hs-CRP resolves the low levels that matter for cardiovascular risk.