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

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
43304-5
Short code
C trach rRNA Spec Ql NAA+probe
Synonyms
C trach rRNA Spec Ql NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
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 doctor may order this test to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate your response to treatment. It can also help identify infections or other inflammatory processes in your body.

What Does a High or Low Level Mean?

Elevated CRP levels often indicate inflammation or infection, while very low levels may suggest no active inflammation. However, results alone don’t diagnose a condition—they’re used alongside other tests and symptoms.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab where it’s separated into serum or plasma for testing. This test doesn’t require fasting.

Common Conditions Monitored

CRP is commonly used to track conditions like rheumatoid arthritis, lupus, heart disease, or infections. It may also be checked after injuries or surgeries to monitor healing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP plays a key role in identifying and managing inflammatory diseases. High levels can signal an ongoing immune response, guiding treatment decisions, such as adjusting medications or planning further tests. However, CRP alone isn’t definitive—it’s part of a broader evaluation.

Short name

CRP (Serum/Plasma)

Frequently asked questions

What causes CRP levels to change?
CRP levels rise in response to infections, injuries, or inflammatory diseases. They can also be affected by certain medications, pregnancy, or other health conditions like obesity or smoking.
How soon will I get my results?
Results are typically available within 24 to 48 hours, depending on your lab’s processing time. Your doctor will discuss the meaning of your results with you.
Can I eat or drink before this test?
No special preparation is needed, including fasting. However, always follow your doctor’s instructions for any specific instructions related to your test.
  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