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C-reactive protein (CRP) by immunoassay (serum/plasma)

Published: August 9, 2026Updated: August 15, 2026

This test measures the level of C-reactive protein, a protein produced by the liver in response to inflammation in your body.

Quick summary

["CRP helps track inflammation, often used to monitor conditions like infections or autoimmune diseases."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
101940-5
Short code
CGLAB
Synonyms
C glabrata DNA Spec Ql NAA+probe
Category
chemistry
Sample
serum
Container
Sterile serum separator tube (SST) or red-top tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
CPT
87481
SNOMED
122450008
Specimen volume
1-2 mL of serum
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days
Hemolysis max
500
Lipemia max
500
Icterus max
40
TAT
24–72 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate responses to treatments. It can also help diagnose infections or identify risks for conditions like heart disease.

What Does a High CRP Level Indicate?

Elevated CRP levels often signal inflammation, which can be caused by infections, injuries, or autoimmune diseases. High levels may also be associated with increased risk for certain chronic conditions, though they don’t always mean a serious problem exists.

What Does a Low CRP Level Indicate?

Low CRP levels typically suggest minimal inflammation. However, very low levels might raise concerns if you have known inflammatory conditions, as they could indicate poor treatment response or undiagnosed issues.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum or plasma, which is then sent to the lab for testing. You may be asked to fast before the test, depending on your provider’s instructions.

Reference range

Negative (Not Detected)N/A

Specimen: serum

No special patient preparation required. Specimen should be collected prior to initiation of antifungal therapy when possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum/Plasma)

Frequently asked questions

How is CRP used in diagnosis and management?
CRP is a useful marker for monitoring inflammation and guiding treatment decisions. It’s often used alongside other tests to assess risk for conditions like cardiovascular disease or to evaluate how well an infection or autoimmune disease is being controlled.
What are the typical reference ranges?
Reference ranges vary by lab and individual health status. Low-risk adults typically have levels below 1 mg/L, while higher levels (above 3 mg/L) may indicate more significant inflammation or risk. Your results will be interpreted by your healthcare provider in the context of your overall health.
Can CRP levels change with diet or lifestyle?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Reducing inflammation through healthy habits may lower CRP, but results depend on overall health and medical conditions.
  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 15, 2026. · Read our editorial policy