CRP Test: How C-Reactive Protein Measures Inflammation
Order CRP Test (C-Reactive Protein)Quick Answer
C-reactive protein is a general marker of inflammation made by the liver. A CRP test can show that inflammation is present, though it does not identify where it comes from.
Key Takeaways
- C-reactive protein is produced by the liver in response to inflammation.
- A standard CRP above about 10 mg/L often signals a significant inflammatory process.
- High-sensitivity CRP uses different ranges to estimate cardiovascular risk.
- An hs-CRP under 1 mg/L is generally considered lower cardiovascular risk.
- CRP is nonspecific and cannot pinpoint the source or cause of inflammation.
- Levels can rise with infection, injury, and inflammatory conditions.
What Is a CRP Test?
A C-reactive protein (CRP) test measures the amount of C-reactive protein in your blood. The liver makes this protein in response to inflammation anywhere in the body. A high result tells a clinician that inflammation is present, but it does not reveal where the inflammation is or what is causing it.
A related test, high-sensitivity CRP (hs-CRP), detects much smaller differences and is used mainly to estimate cardiovascular risk rather than to find acute inflammation.
Standard CRP vs High-Sensitivity CRP
| Test | Main use | Typical interpretation |
|---|---|---|
| Standard CRP | Detect active inflammation or infection | Under 10 mg/L often considered normal |
| hs-CRP | Estimate cardiovascular risk | Under 1 mg/L low, 1 to 3 average, above 3 higher |
The two tests measure the same protein but are calibrated differently. A result that looks alarming on one scale may be unremarkable on the other, so it helps to know which test was run.
Why a CRP Test Is Ordered
- Evaluating symptoms of infection or inflammation
- Monitoring a known inflammatory or autoimmune condition
- Assessing cardiovascular risk when used as hs-CRP
- Following response to treatment for an infection
- Investigating unexplained fever or joint pain
CRP rises within hours of an inflammatory trigger and falls quickly as it resolves, which makes it useful for tracking change over time rather than diagnosing a specific disease.
How to Read Your Results
Because CRP is nonspecific, a single value is rarely enough on its own. A marked rise may point to an infection or a flare of an inflammatory condition, while a mild rise can come from many everyday causes. When hs-CRP is used for heart risk, it is interpreted alongside cholesterol, blood pressure, and other factors.
Keep in mind that normal ranges differ by laboratory and by whether the standard or high-sensitivity assay was used. Compare your number to the range on your own report.
How to Order / Where to Get Tested
You can order a CRP or hs-CRP test directly through a lab-testing service in most states. Select the test online, pay at checkout, and visit a CLIA-certified lab or our partner lab for the blood draw. The sample is a small tube of blood taken from a vein, and the visit usually takes only a few minutes.
Some states require a physician order for direct-access testing, which the service arranges. Results are typically posted to a secure portal within one to two business days.
How Much Does It Cost
A standalone CRP test commonly costs between $15 and $60 through direct-access services, and hs-CRP is often priced in the same range. When it is bundled inside a heart-health or inflammation panel, the total rises with the number of markers included. Insurance and Medicare usually cover CRP when it is ordered to evaluate a medical condition.
How to Prepare
No fasting is required for a CRP test, although some panels that include it may ask you to fast for other markers. Avoid hard exercise and report any recent illness or infection to your clinician, since both can raise CRP temporarily and make results harder to interpret.
Inflammation and Heart Risk
Low-grade inflammation is thought to play a role in the buildup of plaque inside arteries. When hs-CRP is measured, a result under 1 mg/L is often grouped with lower risk, 1 to 3 mg/L with average risk, and above 3 mg/L with higher risk. This is a risk marker, not a diagnosis, and it is used alongside cholesterol and blood pressure.
Because hs-CRP can rise after an infection or injury, a result above 10 mg/L is usually treated as a sign of active inflammation and repeated later before it is used for heart-risk estimation.
What Else Can Raise CRP?
- Bacterial or viral infections
- Inflammatory conditions such as arthritis
- Recent injury, surgery, or intense exercise
- Smoking and excess body weight
- Pregnancy
Because so many things raise CRP, the test is best used to track a known condition or to add context, not to reach a diagnosis on its own. A clinician will consider your symptoms, history, and other lab results before drawing conclusions.
Frequently Asked Questions
What does a high CRP level mean?
It means inflammation is present somewhere in the body. CRP does not identify the source, so it is interpreted with symptoms and other tests.
What is the difference between CRP and hs-CRP?
Both measure C-reactive protein. The high-sensitivity version detects small differences and is used to estimate heart risk, while standard CRP is used to detect active inflammation.
Can stress raise CRP?
Physical stress such as infection, injury, or intense exercise can raise CRP. Ongoing psychological stress has also been linked to mildly higher levels over time.
Do I need to fast for a CRP test?
No, a CRP test does not require fasting. If it is part of a larger panel, follow the fasting instructions for that panel.
How quickly does CRP change?
CRP can rise within hours of an inflammatory trigger and fall within days as the trigger resolves, which is why it is useful for tracking change.
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This guide is reviewed for sourcing accuracy against the references listed above. It is educational information, not medical advice. Always consult a qualified healthcare provider about your own results and care.
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