C-Reactive Protein Test
Category
Immunology
Specimen
Blood (Serum)
Organ System
—
Available At
0 labs
About C-Reactive Protein Test
C-Reactive Protein, commonly known as CRP, is a protein produced by the liver that rises sharply — often within just 6 to 8 hours — in response to inflammation or tissue injury anywhere in the body.
Because CRP responds so quickly and dramatically to inflammation, it's widely used as a general, sensitive marker to detect and track the severity of infections, autoimmune flare-ups, and inflammatory conditions.
Unlike more specific tests that look for one particular disease, CRP doesn't tell your doctor exactly what's causing the inflammation — only that inflammation is present and, through serial testing, whether it's improving or worsening.
This makes CRP especially valuable for monitoring how a patient is responding to treatment for infections or inflammatory diseases, since levels typically fall quickly once the underlying problem resolves.
When Should You Get C-Reactive Protein Test
CRP testing is ordered when there's:
- Suspected bacterial or viral infection
- Unexplained fever
- Monitoring known inflammatory or autoimmune conditions
- Assessing response to antibiotic or anti-inflammatory treatment
- Investigating unexplained joint pain or swelling
Conditions C-Reactive Protein Test Can Detect
Elevated CRP levels are seen in:
- Bacterial and viral infections
- Autoimmune diseases such as rheumatoid arthritis and lupus
- Inflammatory bowel disease
- Recent surgery or significant tissue injury
- Certain cancers
How to Prepare for C-Reactive Protein Test
- No special preparation or fasting is required for a standard CRP test.
- Inform your doctor if you're taking anti-inflammatory medications like NSAIDs or steroids, as these can lower CRP levels and mask the true extent of inflammation.
- A simple venous blood sample is all that's needed.
C-Reactive Protein Test Normal Reference Ranges
| Parameter | Normal Range |
|---|---|
| Normal | Below 1.0 mg/dL (exact cutoffs vary by lab and assay) |
Very high CRP levels (often above 10 mg/dL) typically suggest a significant bacterial infection or major inflammatory flare, while mildly elevated levels can be seen with less serious causes including obesity, smoking, or minor infections.
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Frequently Asked Questions About C-Reactive Protein Test
What's the difference between CRP and hs-CRP?
hs-CRP (high-sensitivity CRP) can detect much smaller elevations than a standard CRP test and is used primarily for assessing long-term cardiovascular risk, whereas standard CRP is used to detect active inflammation or infection.
Does CRP tell my doctor exactly what's wrong?
No — CRP is non-specific, meaning it rises with many different types of inflammation and infection. Your doctor uses it alongside your symptoms and other tests to pinpoint the actual cause.
How quickly does CRP respond to treatment?
CRP levels can fall significantly within just a few days of effective treatment, making it a useful tool for tracking whether an infection or inflammatory flare is responding as expected.
Can CRP be elevated without any obvious illness?
Yes, mild CRP elevation can occur with obesity, smoking, chronic low-grade inflammation, or even after strenuous exercise, so isolated mild elevations aren't always clinically significant.
Medical Disclaimer: This page is for informational purposes only and does not constitute medical advice. Lab test results should always be interpreted by a qualified healthcare professional in the context of your clinical history. Do not self-diagnose or alter your treatment based on test results alone.
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