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C-reactive protein (CRP) – Serum

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

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

Quick summary

["CRP helps track inflammation in your body."]

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

Key facts at a glance

LOINC
42370-7
Short code
N men sg B Ag Islt Ql Aggl
Synonyms
N men sg B Ag Islt Ql Aggl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggl
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 a CRP test to check for signs of inflammation, monitor conditions like arthritis, infections, or heart disease, or evaluate responses to treatments. It can also help diagnose or monitor certain autoimmune diseases or infections.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or hand to draw blood. If you’re on blood thinners, let your provider know before the test.

What to Expect During the Test

The blood sample is taken and sent to a lab for analysis. Results are typically ready within a few days, depending on lab processing times.

What the Results Mean

CRP levels vary. Higher levels may indicate inflammation, infections, or other health issues. Your provider will interpret results in the context of your medical history and symptoms.

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 change?
CRP levels can rise due to infections (like pneumonia or urinary tract infections), injuries, surgeries, or certain medical conditions (like autoimmune diseases). Stress, smoking, or certain medications may also affect CRP levels.
How long does it take to get results?
Results are usually available within 2–5 business days, depending on your lab’s processing schedule. Your provider will discuss them with you during your follow-up visit.
Can CRP levels be affected by diet or exercise?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Eating a heart-healthy diet, staying active, and avoiding smoking may help lower inflammation over time.
  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