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 identify inflammation, often used to monitor conditions like infections or autoimmune diseases."]
Key facts at a glance
- LOINC
- 32672-8
- Short code
- COLDAG
- Synonyms
- CA SerPl Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube (no anticoagulant); serum separator tube (SST) acceptable if maintained at 37°C
- Units
- N/A
- Ref low
- 0
- Ref high
- 63
- Critical range
- — – 1000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Cold agglutinin titer by serial dilution at 4°C
- CPT
- 86157
- SNOMED
- 7924-3
- Specimen volume
- 3-5 mL whole blood to yield at least 1-2 mL serum
- Stability
- Serum must be separated and stored at 37°C if tested within 4 hours; if delayed, serum should be frozen at -20°C or colder. Avoid refrigeration as cold exposure causes false-positive agglutination.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test to check for signs of inflammation, monitor chronic conditions (such as rheumatoid arthritis or heart disease), or evaluate your response to treatment for infections or other illnesses.
What Does a High or Low Level Mean?
Elevated CRP levels often indicate inflammation or infection. Very high levels may suggest severe conditions like sepsis or certain cancers. Low levels might mean your body isn’t responding to inflammation as expected, though this can vary by individual and context.
Common Uses in Healthcare
This test is frequently used to screen for or monitor conditions like heart disease, autoimmune disorders, and infections. It can also help assess how well you’re healing after surgery or injury.
What to Expect Before or After the Test
No special preparation is needed. Blood is drawn from a vein, usually in your arm. You may feel a slight pinch, but it typically takes a few minutes to complete. Results are usually ready within a few days.
Reference range
Negative; titer <1:64 at 4°C is generally considered normal. Titers ≥1:64 may be clinically significant and suggestive of cold agglutinin disease or cold autoimmune hemolytic anemia.N/A
No fasting required. Specimen must be kept at 37°C during collection and transport to prevent cold-induced agglutination and false-positive results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
CRP (Serum/Plasma)
Frequently asked questions
CRP is a marker for inflammation and is often used alongside other tests to guide treatment decisions. While it doesn’t diagnose specific conditions, it helps doctors track overall health and response to treatments by showing whether inflammation is present or improving.
How often should I get this test?
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 16, 2026. · Read our editorial policy