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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 substance 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
80849-3
Short code
Deprecated US Brst-R CN Bx guide
Synonyms
Deprecated US Brst-R CN Bx guide
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us
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 This Test Is Done

Doctors may order CRP testing to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, evaluate infections, or assess risk for heart disease. It can also help guide treatment decisions for conditions like joint pain or after trauma.

What to Expect Before the Test

No special preparation is needed. You may fast before the test, but your doctor will let you know if fasting is required. Bring any medications you’re currently taking to your appointment.

How the Test Works

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

What the Results Mean

Higher-than-normal CRP levels may indicate inflammation, infections, or other health issues. Lower levels suggest minimal inflammation. Your doctor will interpret results in the context of your medical history and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP is a marker for systemic inflammation. Elevated levels can signal infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., lupus, rheumatoid arthritis), or other inflammatory processes. It may also help assess cardiovascular risk or guide treatment adjustments for chronic conditions.

Short name

CRP (Serum)

Frequently asked questions

What causes CRP levels to be high?
CRP levels can rise due to infections (like colds or flu), injuries, surgeries, or certain chronic conditions such as arthritis. Stress, smoking, or certain medications may also temporarily affect CRP levels.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
Can lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Reducing inflammation through healthy eating, regular activity, and avoiding smoking may help lower CRP levels 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