Inflammation Marker

CRP Test (C-Reactive Protein)

CRP is a protein your liver releases in response to inflammation or infection. A high CRP tells your doctor something is inflaming your body, even if you feel fine.

Written and clinically reviewed by Suman Konda, PharmD, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: 01 August 2026 · How we check our content

What is a CRP test?

C-Reactive Protein (CRP) is an acute-phase protein produced by the liver within a few hours of infection, injury or inflammation. It rises rapidly (within 6–12 hours) and falls just as fast when the cause resolves, making it an excellent real-time marker of active inflammation. There are two types of CRP test: standard CRP (for detecting significant inflammation) and high-sensitivity CRP (hsCRP, for assessing heart disease risk at lower levels).

CRP Normal Range

Test Type	Value	Interpretation
Standard CRP: Normal	<10 mg/L	No significant inflammation
Standard CRP: Mild elevation	10 – 50 mg/L	Mild inflammation / viral infection
Standard CRP: Significant	50 – 200 mg/L	Active bacterial infection likely
Standard CRP: Severe	> 200 mg/L	Severe infection / serious condition
hsCRP: Low CV risk	< 1 mg/L	Low cardiovascular risk
hsCRP: Moderate CV risk	1 – 3 mg/L	Moderate CV risk
hsCRP: High CV risk	> 3 mg/L	High cardiovascular risk

What does HIGH CRP mean?

HIGH CRP above 10 mg/L

A high CRP means your body is fighting inflammation. Common causes: bacterial infections (pneumonia, UTI, appendicitis), viral infections (dengue, COVID-19), autoimmune conditions (rheumatoid arthritis, lupus, IBD), post-surgery or injury, heart attack (CRP rises within hours), cancer, and inflammatory bowel disease. The higher the CRP, the more severe the inflammation, though it doesn't tell you WHERE the inflammation is. Your doctor will combine CRP with symptoms and other tests to find the source.

CRP vs hsCRP: what's the difference?

Standard CRP vs High-Sensitivity CRP (hsCRP)

Standard CRP detects significant inflammation (infections, flares). It is not useful for detecting the very low-grade inflammation linked to heart disease. hsCRP (high-sensitivity CRP) measures tiny amounts of CRP and is used specifically to assess long-term cardiovascular risk: a persistently elevated hsCRP of 2–3 mg/L increases heart attack risk even in people with no obvious disease. If your doctor ordered hsCRP (not standard CRP), they are evaluating your heart risk, not looking for infection.

Questions to ask your doctor

Is this standard CRP or hsCRP: and what specifically were you checking for?
What is causing the elevated CRP?
Do I need antibiotics or anti-inflammatory treatment?
When should I recheck to confirm it has come down?

What CRP tells your doctor

C-reactive protein (CRP) is made by the liver and rises quickly when there is inflammation anywhere in the body. It is a sensitive but non-specific marker: it tells you that inflammation is present and roughly how much, but not where or why. This makes it useful for detecting and monitoring infection and inflammatory conditions.

Because CRP rises within hours and falls quickly once the cause settles, it is particularly good for tracking response to treatment, such as whether an infection is improving on antibiotics.

High CRP: what it can mean

A markedly raised CRP most often reflects a bacterial infection, but it also rises in inflammatory conditions such as rheumatoid arthritis, after surgery or injury, and in some other illnesses. A mild elevation can accompany many everyday conditions and is less specific.

Because CRP is non-specific, it is always interpreted alongside symptoms and other tests rather than in isolation. A high-sensitivity version (hs-CRP) is sometimes used differently, to help assess cardiovascular risk.

CRP versus ESR

CRP is often compared with the ESR, another inflammation marker. CRP rises and falls faster, making it better for tracking rapid changes, while ESR responds more slowly and is affected by age and anaemia. Doctors sometimes use both together, as occasionally one is raised when the other is not.

Neither test diagnoses a specific disease; they signal that inflammation is present and guide how actively to investigate or monitor it.

Frequently Asked Questions

Do I need to fast for a CRP test?

No. CRP does not require fasting and can be taken at any time.

What does a high CRP mean?

It indicates inflammation, often from infection, but also from injury, surgery or inflammatory conditions. It shows something is active but not exactly what, so it is read alongside other findings.

How quickly does CRP change?

CRP rises within hours of inflammation starting and falls quickly once it settles, which makes it useful for monitoring response to treatment.

What is the difference between CRP and ESR?

Both measure inflammation, but CRP responds faster and is better for tracking rapid change, while ESR is slower and influenced by age and anaemia.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

C-Reactive Protein: Clinical Relevance and Interpretation. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK441843