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C-reactive protein (CRP) by nephelometry (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 identify inflammation, often used to monitor conditions like infections or autoimmune diseases."]

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

Key facts at a glance

LOINC
94600-4
Short code
EIV Spec Ql Cult
Synonyms
EIV Spec Ql Cult
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
organism-specific-culture
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 CRP Matters in Your Health

CRP is a marker that signals your body’s immune response. High levels may indicate an infection, injury, or inflammation, while low levels suggest minimal inflammation. This test is often used alongside other tests to guide treatment decisions.

Common Uses for CRP Testing

Doctors may order CRP tests to diagnose or monitor conditions such as infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis), or heart disease risk. It can also help assess how well a treatment is working.

What to Expect Before or After the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if instructed. After drawing blood, you may feel slight discomfort, but it typically resolves quickly. Results are usually available within 24–48 hours.

What Your Results Mean

Results are interpreted by your healthcare provider based on your overall health and medical history. Elevated CRP levels may prompt further testing or adjustments to treatment, while normal levels do not rule out inflammation entirely.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Nephelometry)

Frequently asked questions

How long does it take to get CRP test results?
Results are typically ready within 24–48 hours, but timing may vary depending on lab processes and your healthcare provider’s workflow. Your doctor will discuss the results with you during your follow-up visit.
Can I eat or drink before a CRP blood test?
Most CRP tests do not require fasting, but follow your doctor’s specific instructions. If fasting is needed, avoid food or liquids (except water) for 8–12 hours before the test to ensure accurate results.
What causes CRP levels to be high?
High CRP levels can result from infections (like flu or bacterial infections), injuries, autoimmune diseases (such as lupus or rheumatoid arthritis), or other inflammatory conditions. Chronic conditions like heart disease may also contribute. Your doctor will evaluate the cause with additional tests and medical history.
  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