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C-reactive protein (serum/plasma concentration)

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

This test measures the level of C-reactive protein in your blood, which is a marker of inflammation.

Quick summary

["CRP helps doctors assess inflammation, often used to monitor conditions like infections, autoimmune diseases, or after surgery."]

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

Key facts at a glance

LOINC
6919-5
Short code
C trach IgG Titr Ser IF
Synonyms
C trach IgG Titr Ser IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82977
SNOMED
3110003
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 is CRP tested?

Your doctor may order CRP testing to check for signs of inflammation, monitor chronic conditions, or evaluate how your body is responding to illness or treatment. It can also help guide decisions about treatments or further testing.

What does CRP measure?

CRP is a protein produced by your liver in response to inflammation. Higher levels may indicate infections, injuries, or inflammatory diseases, but it can also rise for other reasons, such as stress or certain medications.

How is CRP collected and tested?

A blood sample is drawn from a vein, usually in your arm. The blood is processed to separate serum or plasma, which is then analyzed to measure CRP levels using a sensitive immunoassay method.

Common reasons for testing CRP

Common reasons include diagnosing infections (like pneumonia or sepsis), assessing autoimmune conditions (like rheumatoid arthritis), monitoring heart disease risk, evaluating post-surgery recovery, or checking for signs of inflammation in chronic illnesses.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What does a high CRP level mean?
A high CRP level often signals inflammation, but it doesn’t always pinpoint the exact cause. Your doctor will consider your symptoms, medical history, and other test results to determine what might be going on.
What does a low CRP level mean?
A low CRP level usually means there is little to no inflammation in your body, but it can also happen if inflammation is controlled by treatment or if your body is naturally low in CRP.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, recent infections, medications, or other factors. Regular monitoring may be needed to track changes, especially if you have ongoing 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 16, 2026. · Read our editorial policy