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C-reactive protein (CRP) by nephelometry

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

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

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
35994-3
Short code
CT Foot-L
Synonyms
CT Foot-L
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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, heart disease, or infections, or evaluate responses to treatments. It can also help identify risks for certain health issues, such as heart disease or autoimmune disorders.

What to Expect Before the Test

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

What the Results Mean

Higher CRP levels may indicate inflammation, infections, or other health concerns. Lower levels suggest less inflammation. Your provider will interpret results based on your medical history and symptoms.

Common Conditions Monitored

CRP is often used to monitor conditions like rheumatoid arthritis, lupus, or heart disease. It can also help guide treatment decisions for infections or inflammatory responses.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP is a marker for systemic inflammation and is widely used in clinical settings to assess risk for cardiovascular events, guide antibiotic therapy for infections, and evaluate autoimmune activity. Elevated levels may prompt further testing or adjustments to treatment plans.

Short name

CRP (Nephelometry)

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 medications. They may also be higher in people with chronic conditions like arthritis or heart disease.
How often should I get a CRP test?
Your provider will determine how often you need the test based on your health needs. Some people get it yearly or more frequently if they have ongoing conditions.
Can CRP levels be affected by diet or exercise?
Diet and exercise can influence inflammation levels, but CRP is primarily a blood test result. Your provider will consider overall health factors when interpreting results.
  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