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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 in your body.

Quick summary

["CRP helps doctors track inflammation and identify possible infections or health conditions."]

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

Key facts at a glance

LOINC
68545-3
Short code
nRBC Snv-Rto
Synonyms
nRBC Snv-Rto
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
SNOMED
900000000000003001
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
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 chronic conditions like arthritis or heart disease, or evaluate symptoms such as fever, swelling, or unexplained pain that may suggest an infection or other health issue.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood sample drawn from a vein in your arm, or your urine may be collected for analysis depending on the clinical context.

What the Results Mean

Higher-than-normal CRP levels may indicate inflammation, infections, autoimmune diseases, or other health problems. Lower levels may suggest reduced inflammation. Your results will be interpreted by your healthcare provider based on your overall health and medical history.

Common Conditions Monitored

CRP is often used to monitor conditions such as rheumatoid arthritis, lupus, heart disease, or infections like pneumonia or urinary tract infections. It can also help assess how well treatments are working.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: fluid

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CRP plays a critical role in identifying and managing inflammatory processes. Elevated CRP levels can signal underlying inflammation that may require medical attention, guiding treatment decisions for chronic diseases or infections. It is a useful marker for both diagnosis and ongoing monitoring.

Short name

CRP (Nephelometry)

Frequently asked questions

What causes CRP levels to be higher than usual?
CRP levels can rise due to infections (like colds, flu, or urinary tract infections), injuries, surgeries, or certain medical conditions such as autoimmune diseases (e.g., rheumatoid arthritis) or heart disease. Stress, smoking, and certain medications can also influence CRP levels.
How often should I get this test?
The frequency of CRP testing depends on your health condition and medical needs. Your healthcare provider will determine how often you need this test, whether it’s part of routine check-ups, monitoring a chronic illness, or in response to specific symptoms.
Can diet or lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet, exercise, smoking, and weight can influence CRP levels. Eating a heart-healthy diet, staying active, avoiding smoking, and maintaining a healthy weight may help lower CRP levels and reduce 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