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C-reactive protein (CRP) in serum/plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures a protein produced by your liver in response to inflammation, often used to monitor general inflammation or infection.

Quick summary

["CRP helps track inflammation levels in your body."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
51368-9
Short code
CD79A
Synonyms
CD79a Cells NFr Fld
Category
chemistry
Sample
serum
Container
Sterile body fluid collection container; lavender-top (EDTA) tube preferred for flow cytometry to prevent clotting
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Flow cytometry; Immunofluorescence
CPT
88184
SNOMED
433481002
Specimen volume
1-5 mL of body fluid depending on fluid type and cellularity; minimum 1 mL recommended
Stability
Specimen should be processed within 1-2 hours of collection for optimal cell viability; if delayed, refrigerate at 2-8°C for up to 24 hours
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for signs of inflammation, infection, or other health conditions like autoimmune diseases, heart disease, or kidney problems. High-sensitivity CRP is particularly useful for detecting low-level inflammation that might not be obvious through other tests.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, which usually causes only mild discomfort. If you’re on blood thinners or have a history of bleeding issues, let your provider know before the test.

What the Results Mean

Results are typically reported in milligrams per liter (mg/L). While reference ranges vary by lab, higher than normal levels often indicate inflammation, infection, or other underlying health concerns. Your provider will interpret results in the context of your overall health and symptoms.

Common Conditions Monitored

This test is commonly used to monitor conditions like cardiovascular disease, rheumatoid arthritis, lupus, and other inflammatory diseases. It may also help assess the effectiveness of treatments for these conditions over time.

Reference range

Reported as percentage of total cells or absolute count; reference ranges vary by fluid type and laboratory; typically CD79a-positive cells are absent or minimal in normal body fluidsN/A

Specimen: serum

No special preparation required. Patient should be informed about the body fluid collection procedure. For CSF collection, lumbar puncture procedure explanation should be provided.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CRP is a marker of systemic inflammation. Elevated levels can signal infections, autoimmune disorders, or chronic conditions like heart disease. It’s often used alongside other tests to guide treatment decisions, such as adjusting medications or planning interventions for conditions like coronary artery disease.

Short name

CRP (High-Sensitivity)

Frequently asked questions

What does a high CRP level mean?
A high CRP level suggests your body is actively responding to inflammation or infection. This could mean you have an acute illness (like a cold or infection), a chronic condition (like arthritis or heart disease), or another underlying issue requiring further evaluation. Your provider will discuss this with you and may recommend additional tests or treatments.
Can I eat or drink before this test?
You can eat and drink normally before this test unless your provider has specific instructions. Typically, fasting is not required for CRP tests, but always follow your healthcare provider’s advice.
How long does it take to get my results?
Results are usually available within a few days to a week, depending on your lab. Your provider will contact you once they have the results to discuss them further. If you have concerns, don’t hesitate to ask your provider for updates.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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