CRP (C-Reactive Protein)
Acute-phase protein as inflammation marker for infections and cardiovascular risk
Also known as
Definition
C-reactive protein (CRP) is an acute-phase protein produced in the liver in response to inflammatory stimuli — primarily driven by IL-6. Standard CRP (classic) serves infection diagnostics; high-sensitivity CRP (hsCRP) measures subclinical inflammation and is an independent cardiovascular risk marker. CRP rises within 6–12 hours of inflammation onset and normalizes rapidly (half-life ~19 h) after resolution.
| Parameter | Value |
|---|---|
| Unit | mg/l |
| Reference Range | Standard CRP: < 5 mg/l (infection diagnostics) | hsCRP (cardiovascular risk): < 1 mg/l (low) | 1–3 mg/l (intermediate) | > 3 mg/l (elevated) |
| Optimal Range (lab2go) | hsCRP < 0.5 mg/l (lab2go Optimum Zone — level seen in metabolically healthy, lean non-smokers) |
↓ What a low value means
Very low CRP (< 0.2 mg/l) indicates no systemic inflammation and is desirable. Persistently low CRP is a sign of good metabolic health. A single measurement without inflammatory symptoms is sufficient for risk stratification.
↑ What a high value means
Standard CRP > 5 mg/l: acute inflammation (infection, autoimmune disease, tissue injury). hsCRP 1–3 mg/l: intermediate cardiovascular risk; 3–10 mg/l: high risk and/or subacute inflammation. > 10 mg/l: severe inflammation or infection — NOT suitable for cardiovascular risk assessment.
✓ How to optimize this marker
Anti-inflammatory diet: omega-3 fatty acids (EPA+DHA 2–3 g/day), Mediterranean diet, polyphenols (olive oil, berries, turmeric). Weight reduction (adipose tissue is pro-inflammatory). Regular moderate exercise. Smoking cessation. Sleep optimization. Dental health (periodontitis substantially raises CRP).
When to test
hsCRP: cardiovascular risk screening (in intermediate-risk patients), metabolic syndrome, monitoring inflammatory conditions. Measure at least twice 2 weeks apart (reproducibility); not during acute infections. Standard CRP: infection diagnostics and monitoring.
Frequently asked questions
What is the difference between CRP and hsCRP? +
It is the same protein but with different assay methods and sensitivity ranges. Standard CRP measures in the mg/l range (infections: 10–500 mg/l). High-sensitivity CRP (hsCRP) measures down to 0.1 mg/l and is designed for subclinical inflammation and cardiovascular risk assessment. Always request hsCRP for heart risk screening.
Can gum disease really raise my CRP? +
Yes, significantly. Periodontitis is a chronic bacterial inflammation that substantially elevates systemic CRP (often > 2 mg/l). Dental treatment measurably normalizes hsCRP. Oral health is an underappreciated factor in cardiovascular risk reduction.
Is CRP a causal factor for heart disease or just a marker? +
Current evidence (Mendelian randomization studies) suggests CRP is primarily a marker of underlying inflammatory processes rather than a direct causal molecule. The elevated cardiovascular risk associated with high hsCRP likely reflects the underlying inflammation (e.g., atherosclerotic plaques, adipose tissue inflammation).
Does exercise permanently lower CRP? +
Yes. Regular moderate aerobic exercise (> 150 min/week) lowers hsCRP by approximately 20–30% long-term. Acute intense exercise (marathon) transiently raises CRP substantially. Mechanism: exercise reduces visceral fat (IL-6 source), improves endothelial function, and increases anti-inflammatory cytokines.
Sources
- Ridker PM et al. (2002) Comparison of C-Reactive Protein and Low-Density Lipoprotein Cholesterol Levels in the Prediction of First Cardiovascular Events. N Engl J Med.
- Pearson TA et al. (2003) Markers of Inflammation and Cardiovascular Disease: AHA/CDC Scientific Statement. Circulation.
- Pepys MB, Hirschfield GM (2003) C-reactive protein: a critical update. J Clin Invest.
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.