C-reactive protein (CRP) concentration, serum/plasma
This test measures the level of C-reactive protein, a protein produced by the liver in response to inflammation in your body.
["CRP helps identify and monitor inflammation, often used to check for infections, autoimmune conditions, or other health issues."]
Key facts at a glance
- LOINC
- 9934-1
- Short code
- Q wave Dpth L-V4
- Synonyms
- Q wave Dpth L-V4
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ekg
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why CRP Matters in Your Health
CRP is a marker that signals your body is fighting inflammation. High levels may indicate infections like pneumonia or urinary tract infections, or conditions such as rheumatoid arthritis or heart disease. Your doctor may order this test to assess risk, track treatment progress, or investigate unexplained symptoms.
When This Test Is Done
CRP tests are often performed during routine check-ups, after an injury or surgery, or when symptoms like fever, joint pain, or fatigue appear. Doctors may also use it to monitor chronic conditions like heart disease or autoimmune disorders.
How the Test Works
A small blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it is analyzed to measure CRP levels. The test is quick and typically done without preparation.
What to Expect Before or After the Test
You may need to fast for 8–12 hours before the test if instructed, but CRP tests often don’t require fasting. After the draw, you might feel slight discomfort at the injection site, but it usually goes away quickly. Avoid strenuous activity for a few hours afterward.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated CRP levels often point to inflammation, which can be caused by infections, injuries, or inflammatory diseases. While CRP alone doesn’t diagnose a specific condition, it helps guide further testing or treatment decisions. Low or normal levels suggest minimal inflammation, but they don’t rule out all causes of symptoms.
Short name
CRP
Frequently asked questions
What does a high CRP level mean?
What does a low CRP level mean?
Can CRP levels change with diet or exercise?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy