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C-reactive protein (CRP) concentration in serum/plasma

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

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

Quick summary

["CRP helps doctors assess inflammation in your body."]

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

Key facts at a glance

LOINC
44992-6
Short code
C trach C IgG Ser Ql
Synonyms
C trach C IgG Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 This Test Done?

Your healthcare provider may order this test to check for signs of inflammation, infection, or other health conditions like heart disease, autoimmune disorders, or kidney problems. It can also be used to monitor treatment progress for conditions causing chronic inflammation.

What Does a High or Low CRP Level Mean?

A higher CRP level often indicates inflammation, which can be linked to infections, injuries, or diseases like rheumatoid arthritis or lupus. A low level usually means less inflammation is present, but it doesn’t rule out all causes of inflammation.

How Is This Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed to measure CRP levels using an immunoassay method.

What Are Common Reference Ranges?

Reference ranges can vary by lab and may not apply to everyone. Typically, normal CRP levels are below 3 mg/L, but values can differ based on individual health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What causes CRP levels to be high?
Common causes of elevated CRP include infections (like pneumonia or urinary tract infections), injuries, surgeries, certain medications, or underlying conditions such as autoimmune diseases (like rheumatoid arthritis) or heart disease. Stress and smoking can also temporarily increase CRP levels.
What if my CRP level is normal but I still feel unwell?
A normal CRP level doesn’t always mean you’re healthy. Other tests or symptoms may be needed to identify the cause of your ongoing discomfort. Your healthcare provider may recommend additional tests or a different approach to diagnosis.
How often should I get this test?
The frequency of CRP testing depends on your medical condition and treatment plan. If you have a chronic illness like arthritis or heart disease, your provider may recommend regular monitoring. If you’re healthy, this test is usually not routinely recommended unless you have specific risk factors or symptoms.
  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