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C-reactive protein (CRP) by nephelometry

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.

Quick summary

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

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

Key facts at a glance

LOINC
35942-2
Short code
CT Ankle-L
Synonyms
CT Ankle-L
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
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?

Doctors may order CRP testing to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate responses to treatments. It can also help diagnose infections or identify risks for conditions like heart disease or certain cancers.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s done on an empty stomach, but this depends on the lab’s protocol. Bring any medications you’re taking to your appointment.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it’s usually over quickly. The blood sample is then sent to the lab for analysis.

What Are Possible Results?

Results are reported in milligrams per liter (mg/L). Higher than normal levels may indicate inflammation, infection, or other health issues. Your doctor will interpret the result in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP (Nephelometry)

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, autoimmune diseases (like rheumatoid arthritis), or other conditions. It’s not specific to any single disease but can guide treatment decisions.
What Does a Low CRP Level Mean?
Low CRP levels usually mean there’s little to no inflammation. However, very low levels might raise concerns if you have a known inflammatory condition, as they could indicate poor treatment response or underlying issues.
How Often Should I Get This Test?
Your doctor will determine how often you need CRP testing based on your medical history, symptoms, and treatment plan. Regular monitoring may be part of managing chronic conditions like heart disease or arthritis.
  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