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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 your liver in response to inflammation or infection in your body.

Quick summary

["CRP helps doctors assess inflammation, track infections, or monitor conditions like arthritis or heart disease."]

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

Key facts at a glance

LOINC
49454-2
Short code
VZV DNA # Amn NAA+probe
Synonyms
VZV DNA # Amn NAA+probe
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why CRP Matters in Your Health

CRP is often checked when you have symptoms like fever, pain, or swelling, or if your doctor suspects an infection, autoimmune condition, or inflammation. It can also be used to monitor long-term conditions like heart disease or rheumatoid arthritis.

When This Test Might Be Ordered

Your doctor may order CRP testing if you have signs of inflammation, such as joint pain, fever, or redness, or if you have a known condition that affects inflammation levels. It’s sometimes used before or after surgery, during pregnancy, or to check for infections like pneumonia.

What to Expect During the Test

A small needle will be used to draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause much discomfort. The blood is then sent to a lab for testing.

Possible Results and Next Steps

High CRP levels may indicate inflammation, infection, or an autoimmune condition. Low levels might suggest no active inflammation. Your doctor will discuss the results with you and decide if further testing or treatment is needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum/Plasma)

Frequently asked questions

What does a high CRP level mean?
A high CRP level often signals inflammation in your body, which can be caused by infections (like a bacterial or viral illness), autoimmune diseases (like lupus or rheumatoid arthritis), or other conditions causing tissue damage.
What does a low CRP level mean?
A low CRP level usually means there isn’t much inflammation detected in your bloodstream. However, it doesn’t rule out other conditions, so your doctor may still recommend further testing if needed.
Can CRP levels change over time?
Yes, CRP levels can change based on your health status, recent infections, medications, or other factors like stress or diet. Your doctor will consider these factors when interpreting your 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