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 doctors assess inflammation, often used to monitor conditions like infections, autoimmune diseases, or after surgery."]
Key facts at a glance
- LOINC
- 37639-2
- Short code
- XR Neck Views
- Synonyms
- XR Neck Views
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 22
- Ref high
- 198
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- xr
- CPT
- 82553
- 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 Is This Test Done?
Your healthcare provider may order a CRP test to check for signs of inflammation. This could be due to infections (like pneumonia or urinary tract infections), autoimmune conditions (such as rheumatoid arthritis), or other health concerns like heart disease or cancer. It may also be used before or after surgery to monitor healing or response to treatment.
What Does a High or Low CRP Level Mean?
Elevated CRP levels often indicate inflammation. Very high levels might suggest severe infections, infections spreading to other parts of the body, or certain autoimmune diseases. Very low levels may suggest no active inflammation, but they can also be seen in some chronic conditions or during recovery from illness.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The blood is then sent to a lab where it is analyzed to measure CRP levels using a sensitive detection method.
What Are Common Results and Next Steps?
Results are typically reported in milligrams per liter (mg/L). If your CRP level is higher than expected, your doctor may recommend further tests or treatments to address the underlying cause. If it’s within normal ranges, they may continue monitoring or adjust your treatment plan accordingly.
Reference range
Adult males: 22-198 U/L; Females: 22-198 U/LN/A
No special preparation required. Inform provider of any chest pain or symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
CRP is a marker for inflammation and is widely used in clinical settings to guide treatment decisions. It can help doctors identify and manage conditions that cause inflammation, reduce unnecessary treatments, and monitor the effectiveness of therapies. While CRP doesn’t diagnose specific conditions, it often points to areas needing further investigation or intervention.
Short name
CRP (Serum/Plasma)
Frequently asked questions
What causes CRP levels to be higher than usual?
How often should I get a CRP test?
Can CRP levels change quickly, or do they take time to return to normal?
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 17, 2026. · Read our editorial policy