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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, a protein produced by the liver in response to inflammation in your body.

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
14634-0
Short code
CRP Titr SerPl
Synonyms
CRP Titr SerPl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
86140
SNOMED
396252006
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

What Is C-Reactive Protein Used For?

CRP is primarily used to detect and monitor inflammation. High levels may signal infections, injuries, or conditions like rheumatoid arthritis or heart disease. It can also help guide treatment decisions, such as adjusting medications for autoimmune disorders or evaluating recovery after surgery.

When Might You Need This Test?

Your doctor may order a CRP test if you have symptoms like fever, joint pain, or unexplained swelling. It’s also used in routine check-ups for people at higher risk of heart disease or autoimmune conditions, or after procedures to monitor healing.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure CRP levels. Results are typically ready within a few days.

What Do Results Mean?

Results show whether your CRP levels are within normal ranges or elevated. Elevated CRP doesn’t always mean an immediate problem, but it can signal inflammation that needs further investigation.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

Why might my CRP be checked?
Your doctor may check CRP to rule out infections, track chronic conditions like arthritis, or assess risks for heart disease. It’s also useful for monitoring treatment responses in autoimmune diseases.
What causes CRP to be high?
Elevated CRP can result from infections (like pneumonia or urinary tract infections), injuries, surgeries, or autoimmune diseases. Stress, smoking, or certain medications can also influence levels.
How long does it take to see results?
Results are usually available within 1–3 business days, depending on lab processing times. Your doctor will discuss them with you during your follow-up.
  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