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C-reactive protein (CRP) concentration in serum

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

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

Quick summary

["Helps assess inflammation, infection, or other health conditions."]

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

Key facts at a glance

LOINC
17620-6
Short code
Deprecated S pneum18c Ab sp1 Ser-aCnc
Synonyms
Deprecated S pneum18c Ab sp1 Ser-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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?

C-reactive protein (CRP) is a protein that your immune system produces as part of the body’s response to inflammation. It can rise in response to infections, injuries, or other conditions that trigger inflammation, such as autoimmune diseases or certain types of heart disease. This test helps doctors monitor how your body is responding to these triggers.

Why Might You Need This Test?

Your doctor may order this test to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, evaluate heart health, or assess how well a treatment is working for conditions like infections or autoimmune diseases.

How Is the Test Done?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is processed to measure CRP levels. The test typically takes a few hours to complete.

What Do My Results Mean?

Results are usually reported in milligrams per liter (mg/L) or micrograms per milliliter (µg/mL). Higher levels may indicate inflammation, infection, or other health concerns, but interpretation depends on your overall health and symptoms. Your doctor will discuss the results with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum)

Frequently asked questions

What causes CRP levels to change?
CRP levels can rise due to infections (like colds or flu), injuries, surgeries, or certain medications. Chronic conditions such as arthritis, heart disease, or autoimmune disorders may also lead to higher CRP levels. Lifestyle factors like stress, poor diet, or lack of exercise can sometimes influence inflammation levels too.
How long does it take to get results?
Test results are usually available within 24 to 48 hours, depending on your lab’s processing schedule. Your doctor will contact you once the results are ready to discuss them further.
Can CRP levels be affected by diet or exercise?
Yes, lifestyle factors like diet (e.g., Mediterranean diet), exercise, and weight management can influence inflammation levels. Reducing processed foods, increasing omega-3 fatty acids, and staying physically active may help lower CRP levels over time. However, individual responses vary, and diet changes should be discussed with your healthcare provider.
  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