C-reactive protein (CRP) in serum/plasma
This test measures the level of C-reactive protein, a protein produced by your 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
- 49229-8
- Short code
- nRBC Fld-Rto
- Synonyms
- nRBC Fld-Rto
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- 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 for inflammation, which is your body’s way of responding to injury, infection, or illness. High levels may signal conditions like infections, arthritis, or other inflammatory diseases.
When This Test Is Ordered
Your doctor may order CRP testing to check for infections, monitor chronic conditions like rheumatoid arthritis, evaluate symptoms of inflammation, or assess recovery after surgery or illness.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours if your test involves blood drawn from a vein. Avoid strenuous activity or aspirin (if advised) 24 hours before testing.
Common Causes of High or Low CRP Levels
High CRP levels can occur with infections (like pneumonia or urinary tract infections), autoimmune diseases (such as lupus or rheumatoid arthritis), or conditions like heart disease. Very low levels may indicate no active inflammation, but they can also be affected by medications or certain health conditions.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
CRP is a key tool for diagnosing and managing inflammatory diseases. It helps doctors track how well treatments are working and identify potential flare-ups early. While not specific to one condition, it provides a broad picture of systemic inflammation.
Short name
CRP (Serum/Plasma)
Frequently asked questions
What does a CRP test tell me about my health?
Can I eat or drink before my CRP test?
How long does it take to get CRP test 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 17, 2026. · Read our editorial policy