C-reactive protein (CRP) concentration in 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 track inflammation, often used to monitor conditions like infections, injuries, or autoimmune diseases."]
Key facts at a glance
- LOINC
- 19170-0
- Short code
- CEAFLD
- Synonyms
- CEA Plr-sCnc
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile, leak-proof, screw-cap container or vacutainer tube without anticoagulant for chemistry analysis; red-top vacutainer acceptable
- Units
- N/A
- Ref low
- 0
- Ref high
- 5
- Critical range
- — – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Immunoassay (chemiluminescent or electrochemiluminescent)
- CPT
- 82378
- SNOMED
- 395125000
- Specimen volume
- 5-10 mL of pleural fluid; minimum 2 mL required for analysis
- Stability
- Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days; Room temperature: 24 hours
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 25
- TAT
- 4–24 hours
- Order
- routine
Why CRP Matters
CRP is a marker that signals inflammation. Your doctor may order this test to check for signs of infection, inflammation, or other health issues, especially if you have symptoms like fever, pain, or swelling.
When You Might Need This Test
You may need a CRP test if you have symptoms of inflammation, such as joint pain, fever, or unexplained weight loss. It’s also used before and after treatments like chemotherapy or surgeries to monitor how your body responds.
What to Expect Before the Test
No special preparation is usually needed, but your doctor might ask you to stop certain medications (like NSAIDs) that can affect CRP levels for a few days before testing.
What Happens During the Test
A small needle will be used to draw blood from a vein in your arm. The process is quick and usually causes only mild discomfort. The blood sample is then sent to a lab for testing.
Reference range
NCBI: CEA <5 ng/mL (non-smokers <2.5)N/A
No special patient preparation required prior to thoracentesis. Inform patient of procedure risks including pneumothorax, bleeding, and infection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
CRP levels can rise sharply during infections (like pneumonia or urinary tract infections), injuries, or autoimmune conditions (like rheumatoid arthritis). While high CRP doesn’t always mean an infection, it can guide treatment decisions. Very low levels may indicate chronic inflammation is under control or that you have a low-risk condition.
Short name
CRP
Frequently asked questions
What does a high CRP level mean?
What if my CRP level is normal?
Can diet or exercise affect CRP levels?
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