C-reactive protein (CRP) by nephelometry (serum/plasma)
This test measures the level of C-reactive protein, a protein made by your liver in response to inflammation.
["CRP helps track inflammation in your body."]
Key facts at a glance
- LOINC
- 107046-5
- Short code
- CD4FLOW
- Synonyms
- CD3-CD4+ NFr Bld FC
- Category
- chemistry
- Sample
- whole-blood
- Container
- EDTA (purple-top) or ACD (yellow-top) anticoagulated whole blood tube; heparinized tubes may be acceptable depending on laboratory protocol
- Units
- N/A
- Ref low
- 500
- Ref high
- 1500
- Critical range
- 200 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- flow-cytometry
- CPT
- 86359
- SNOMED
- 3921000175106
- Specimen volume
- 1–3 mL of whole blood (minimum 0.5 mL for pediatric samples)
- Stability
- Ambient temperature: process within 24 hours (preferably within 6–8 hours). Refrigerated (2–8°C): up to 24–48 hours. Do not freeze. Specimen stability is highly time-sensitive due to cell viability concerns.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test to check for signs of inflammation, monitor conditions like infections, autoimmune diseases, or after certain treatments. It can also help evaluate risk for heart disease or other inflammatory conditions.
What Does a High or Low CRP Level Mean?
Elevated CRP levels often indicate inflammation, which can be caused by infections, injuries, or diseases like rheumatoid arthritis or lupus. Very low levels may suggest no active inflammation, but this isn’t always reliable alone.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed using nephelometry, a method that measures how much light is scattered by particles in the blood.
What Should You Do Before the Test?
Avoid strenuous exercise or heavy meals 24 hours before the test. If you’re taking medications that affect inflammation, let your provider know.
Reference range
Adult reference range: 500–1500 cells/μL (approximately 30–60% of total lymphocytes). Reference ranges vary by laboratory and age; pediatric values differ with age.N/A
No fasting required. Patient should be well-hydrated. Avoid recent corticosteroid, immunosuppressive, or immunomodulatory therapy if clinically feasible, as these may alter lymphocyte subset counts. Inform the laboratory of recent blood transfusions, vaccinations, or active infections.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
CRP (NONE)
Frequently asked questions
What are the typical reference ranges for CRP?
Does CRP change with age or gender?
Can diet or lifestyle 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