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C-reactive protein (CRP) by nephelometry

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

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

Quick summary

["CRP helps doctors assess inflammation in your body."]

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

Key facts at a glance

LOINC
103037-8
Short code
Codfish (rGad c) 1 IgE RAST
Synonyms
Codfish (rGad c) 1 IgE 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 healthcare provider may order this 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 diseases, such as cardiovascular issues.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into a vein in your arm to draw blood. If you’re concerned about needles, let your healthcare provider know.

What the Results Mean

Higher than expected levels may suggest inflammation, infection, or other health issues. Lower levels might indicate no active inflammation. Your results will be discussed with you by your provider.

Common Conditions Monitored

This test is often used to monitor conditions like rheumatoid arthritis, heart disease, or infections. It can also help track how well certain treatments are working.

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 (Nephelometry)

Frequently asked questions

What causes CRP levels to change?
CRP levels can rise due to infections (like colds or flu), injuries, surgeries, or certain medical conditions like arthritis or heart disease. Stress, smoking, or certain medications may also affect levels.
How often should I get this test?
Your provider will determine how often you need this test based on your health needs. Some people get it yearly, while others may need it more often if they have ongoing health conditions.
Can diet or lifestyle affect CRP levels?
Yes, diet and lifestyle choices like exercise, smoking, and weight management can influence CRP levels. Eating a heart-healthy diet, staying active, and avoiding smoking may help lower inflammation.
  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