C-reactive protein (CRP) in serum/plasma
This test measures the level of C-reactive protein, a protein produced by the liver in response to inflammation or infection in your body.
["CRP helps doctors assess inflammation and identify possible infections or conditions causing swelling."]
Key facts at a glance
- LOINC
- 31048-2
- Short code
- C immitis Ab Fld Ql CF
- Synonyms
- C immitis Ab Fld Ql CF
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- comp-fix
- 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
What Is C-Reactive Protein Used For?
CRP is commonly used to monitor inflammation in conditions like arthritis, heart disease, or after surgery. It can also help detect infections, such as pneumonia or urinary tract infections, especially in people with weakened immune systems. Some doctors use it to track how well treatments are working for chronic inflammatory diseases.
Why Might You Need This Test?
Your doctor may order a CRP test if you have symptoms of inflammation, such as fever, pain, or swelling, or if you’re at risk for conditions like heart disease or autoimmune disorders. It’s also used in certain screening or follow-up situations, like after a heart attack or before surgery.
How Is the Test Done?
A blood sample is taken from a vein, usually in your arm. The blood is sent to a lab where it’s analyzed to measure CRP levels. The test typically takes a few hours to complete, and results are usually available within a day or two.
What Do My Results Mean?
Results can vary widely depending on your health status. Very high levels may indicate severe inflammation or infection, while very low levels might suggest no active inflammation. Your doctor will interpret the results in the context of your symptoms and medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: CRP plays a key role in identifying and monitoring inflammation across many diseases. It’s a useful marker for guiding treatment decisions, assessing disease activity, and evaluating response to therapy in conditions like rheumatoid arthritis, cardiovascular disease, or sepsis. However, it’s not always definitive on its own and is often used alongside other tests.
Short name
CRP (Serum/Plasma)
Frequently asked questions
What causes CRP levels to be high?
How often should I get this test?
Can CRP levels be affected by diet or lifestyle?
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