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C-reactive protein (CRP) by nephelometry (plasma)

Published: August 9, 2026Updated: August 16, 2026

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

Quick summary

["CRP helps track inflammation, often used to monitor conditions like infections, autoimmune diseases, or after surgery."]

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

Key facts at a glance

LOINC
19228-6
Short code
DO-Hgb MFr BldMV
Synonyms
DO-Hgb MFr BldMV
Category
hematology
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
12
Ref high
17.5
Critical range
7 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85018
SNOMED
900000000000003004
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order CRP testing to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, or evaluate how your body is responding to treatment for infections or injuries. It can also help assess risk for heart disease or other inflammatory disorders.

What to Expect Before the Test

No special preparation is needed for this blood test. You may fast for 8–12 hours before the draw if instructed by your provider, but this is not always required for CRP. Bring any medications or supplements you’re taking, as some may affect results.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The blood is then sent to a lab for analysis using nephelometry, a precise method to measure protein levels.

What Are Possible Results?

Results are reported in milligrams per deciliter (mg/dL). Higher than normal levels may indicate inflammation, infection, or other health issues. Your provider will interpret results in the context of your medical history and symptoms.

Reference range

Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A

Specimen: whole-blood

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP (Plasma)

Frequently asked questions

What does a high CRP level mean?
A high CRP level often signals inflammation in your body. It can help doctors diagnose conditions like infections (e.g., pneumonia), autoimmune diseases (e.g., lupus), or assess how well treatments are working. However, CRP alone isn’t diagnostic—it’s used alongside other tests and symptoms.
What does a low CRP level mean?
Low CRP levels usually mean there’s little to no inflammation. This could be normal if you’re healthy, but it may also indicate conditions like certain types of arthritis or other inflammatory disorders that require further evaluation.
Can CRP levels change with diet or exercise?
Yes, lifestyle factors like diet, exercise, and smoking can influence CRP levels. For example, a healthy diet rich in fruits, vegetables, and omega-3s may help lower CRP. However, CRP is primarily a marker of inflammation, not a direct measure of diet or activity levels.
  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