CRP (C-Reactive Protein)
A blood test that measures the level of C-reactive protein, a marker of inflammation in the body.
Last medically reviewed: April 10, 2026 | Reviewed by LabResult.MD Editorial Team
What is CRP?
C-reactive protein (CRP) is a substance produced by the liver in response to inflammation. When there is inflammation somewhere in the body — whether from an infection, injury, or chronic disease — CRP levels in the blood rise rapidly, sometimes within hours.
CRP is a general marker of inflammation and does not point to a specific location or cause. A high-sensitivity CRP (hs-CRP) test can detect lower levels of CRP and is often used to assess cardiovascular disease risk, while a standard CRP test is used to detect more significant levels of inflammation.
Why Is It Tested?
A healthcare provider may order a CRP test to:
- Detect or monitor inflammation from infections or chronic diseases
- Assess cardiovascular disease risk (using hs-CRP)
- Monitor treatment effectiveness for autoimmune conditions (rheumatoid arthritis, lupus)
- Evaluate suspected infections or sepsis
- Monitor post-surgical recovery for signs of infection
- Help differentiate between bacterial and viral infections
Normal Reference Ranges
Reference ranges may vary by laboratory, testing method, age, and other factors. Always use the ranges provided on your lab report.
| Test Type | Level | Interpretation |
|---|---|---|
| Standard CRP | Less than 10 mg/L | Normal |
| 10 mg/L or higher | Elevated — suggests significant inflammation | |
| hs-CRP (cardiovascular risk) | Less than 1.0 mg/L | Low cardiovascular risk |
| 1.0 – 3.0 mg/L | Average cardiovascular risk | |
| Greater than 3.0 mg/L | Higher cardiovascular risk |
What Does a High CRP Level Mean?
High CRP indicates that there is inflammation somewhere in the body. The level can help suggest the severity:
- Mild elevation (10–40 mg/L): Moderate inflammation, often from viral infections or mild inflammatory conditions
- Moderate elevation (40–200 mg/L): Significant inflammation, often from bacterial infections or active autoimmune disease flares
- Severe elevation (above 200 mg/L): Major infections (sepsis), severe burns, or acute trauma
Common causes of elevated CRP include infections (bacterial, viral, fungal), autoimmune diseases (rheumatoid arthritis, inflammatory bowel disease), tissue injury or trauma, heart attack, cancer, obesity, and smoking.
What Does a Low CRP Level Mean?
Low CRP levels are normal and generally indicate that there is no significant inflammation present in the body. A low hs-CRP is also favorable for cardiovascular risk assessment.
There is no clinical concern associated with a low CRP result. It simply means the body is not currently mounting a significant inflammatory response.
Common Next Steps
Depending on the result, a healthcare provider may recommend:
- Additional testing to identify the source of inflammation (blood cultures, imaging, autoimmune panels)
- ESR (erythrocyte sedimentation rate) to complement the CRP results
- Repeat CRP testing to monitor response to treatment
- Lipid panel and other cardiovascular risk assessments if hs-CRP is elevated
- Lifestyle modifications (exercise, diet, smoking cessation) to reduce chronic inflammation
- Anti-inflammatory medications or treatment of the underlying condition
Frequently Asked Questions
What is a normal CRP level?
For a standard CRP test, levels below 10 mg/L are considered normal. For hs-CRP used to assess cardiovascular risk, the American Heart Association defines low risk as less than 1.0 mg/L, average risk as 1.0–3.0 mg/L, and high risk as above 3.0 mg/L.
What is the difference between CRP and hs-CRP?
Both measure C-reactive protein, but hs-CRP (high-sensitivity CRP) can detect much lower levels. Standard CRP detects significant inflammation from infections or autoimmune diseases. hs-CRP assesses cardiovascular disease risk by detecting low-grade inflammation.
Can CRP be elevated without infection?
Yes. CRP can be elevated due to autoimmune conditions, obesity, smoking, chronic stress, tissue injury, and cardiovascular inflammation. It is a nonspecific marker — it indicates inflammation is present but does not identify the cause.
Related Tests and Biomarkers
Sources
- American Heart Association. Inflammation and Heart Disease (2024)
- MedlinePlus. C-Reactive Protein (CRP) Test. U.S. National Library of Medicine
- Ridker PM. C-Reactive Protein and the Prediction of Cardiovascular Events. New England Journal of Medicine
Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Reference ranges vary by laboratory. Always discuss your results with a qualified healthcare provider.