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C-reactive protein (CRP) by nephelometry

Published: August 9, 2026Updated: August 17, 2026

This test measures a protein in your blood that rises when your body is fighting inflammation or infection.

Quick summary

["High CRP levels may signal inflammation, which can help track conditions like infections or autoimmune diseases."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
102931-3
Short code
D farinae IgG4 RAST
Synonyms
D farinae IgG4 RAST
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
rast
CPT
84484
SNOMED
302774002
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 doctor may order this test to check for signs of inflammation, monitor chronic conditions (such as arthritis or heart disease), or evaluate responses to treatments. High-sensitivity CRP is often used to detect early inflammation that standard CRP might miss.

What Does a High or Low Level Mean?

Elevated levels may indicate inflammation, infections, or certain autoimmune disorders. Lower-than-normal levels might suggest reduced inflammation, but they don’t always mean you’re healthy.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed using a special technique called nephelometry to measure CRP levels precisely.

Common Conditions Monitored

This test is commonly used to monitor conditions like rheumatoid arthritis, cardiovascular disease, or infections. It can also help assess how well treatments are working for inflammatory conditions.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (High-Sensitivity)

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 affected by stress, smoking, or certain chronic conditions like heart disease or arthritis.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition and treatment plan. Regular monitoring may be needed for conditions like autoimmune diseases or heart disease.
Can lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. Reducing inflammation through healthy habits may lower CRP, but results vary by individual.
  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 17, 2026. · Read our editorial policy