Skip to content

C-reactive protein (CRP) mass concentration in serum

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

This test measures the level of C-reactive protein in your blood, a marker often used to assess inflammation or infection.

Quick summary

["CRP helps doctors track inflammation, which may signal infections, autoimmune conditions, or other health concerns."]

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

Key facts at a glance

LOINC
28553-6
Short code
Deprecated S pneum6+26 Ab sp1 Ser-mCnc
Synonyms
Deprecated S pneum6+26 Ab sp1 Ser-mCnc
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

Why It’s Done

Your healthcare provider may order this test to check for signs of inflammation, monitor conditions like rheumatoid arthritis or heart disease, or evaluate responses to treatments. It can also help diagnose infections, such as pneumonia or sepsis, or identify risks for complications like heart attacks or strokes.

What to Expect

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch, but it typically doesn’t cause discomfort afterward. Results are usually available within a few days.

Normal vs. Abnormal Results

While reference ranges vary by lab, higher CRP levels often indicate increased inflammation. Your results will be compared to your specific lab’s standards and discussed with your provider.

Common Conditions Monitored

Elevated CRP is commonly seen in infections (e.g., bacterial or viral), autoimmune diseases (e.g., lupus, arthritis), or after injuries/surgeries. Low or normal levels may suggest no active inflammation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum)

Frequently asked questions

How long does it take to get my CRP results?
Results are typically ready within 2–5 business days, depending on your lab’s processing time. Your healthcare provider will contact you once they’re available.
Can I eat or drink before this test?
For most CRP tests, fasting isn’t required. However, always follow your provider’s instructions, as some labs may have specific guidelines (e.g., avoiding certain medications).
Does CRP change with age?
Yes, CRP levels can vary with age and health status. Older adults may naturally have slightly higher baseline levels, but elevated readings still signal inflammation or risk factors that need evaluation.
  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