C-reactive protein (CRP) by nephelometry (serum/plasma)
This test measures a protein called C-reactive protein, which your body produces in response to inflammation. It’s often used to check for signs of infection, injury, or other inflammatory conditions.
["CRP helps doctors monitor inflammation levels in your blood."]
Key facts at a glance
- LOINC
- 31281-9
- Short code
- CARAB
- Synonyms
- CAR Ab Ser Ql
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red top tube
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Immunofluorescence Assay (IFA) or Western Blot
- CPT
- 86255
- SNOMED
- 395112001
- Specimen volume
- 1-2 mL serum
- Stability
- Stable for 7 days at 2-8°C; for longer storage, freeze at -20°C or below
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 72–168 hours
- Order
- routine
Why Might You Need This Test?
Your healthcare provider may order a high-sensitivity CRP test if you have symptoms like fever, pain, or swelling, or if you’re at risk for conditions like heart disease, autoimmune disorders, or infections. It can also help track how well treatments for inflammation are working.
What to Expect During the Test
A small needle will be used to draw blood from a vein, usually in your arm. The blood sample is then sent to a lab for testing. The process usually takes a few minutes, and you may feel a brief pinch or slight discomfort.
What the Results Mean
Higher than normal CRP levels may indicate inflammation, but they can also be influenced by factors like stress, recent illness, or certain medications. Your results will be interpreted by your healthcare provider based on your overall health and medical history.
Common Reasons for Testing
Doctors often use CRP to assess conditions like rheumatoid arthritis, lupus, or heart disease. It can also help diagnose infections, such as pneumonia or sepsis, and guide decisions about treatments like steroids or antibiotics.
Reference range
NegativeN/A
No special preparation required. Patient should inform clinician of any current immunosuppressive therapy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: CRP is a marker for systemic inflammation. While it doesn’t pinpoint the exact cause of inflammation, elevated levels can signal underlying issues that require further evaluation, such as infections, autoimmune diseases, or chronic conditions like heart disease. Your provider will use these results alongside other tests and symptoms to make a diagnosis or treatment plan.
Short name
CRP (High Sensitivity)
Frequently asked questions
What does a high CRP level mean?
Can I eat or drink before this test?
How long will it take to get my results?
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