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C-reactive protein (CRP) measured by nephelometry in serum/plasma

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

This test checks for inflammation in your body by measuring a protein called C-reactive protein, which rises when tissues are injured or infected.

Quick summary

["CRP helps identify 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
6509-4
Short code
N men rRNA CSF Ql Probe
Synonyms
N men rRNA CSF Ql Probe
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why CRP Matters in Your Health

CRP is a marker produced by your liver in response to inflammation. It doesn’t specifically indicate where the inflammation is occurring but helps doctors track overall body response to injury, infection, or disease activity. This test is often used alongside other tests to guide treatment decisions.

When This Test Is Ordered

Your doctor may order CRP testing if you have symptoms like fever, pain, or swelling; if you’re recovering from surgery or an illness; or if you have conditions like arthritis, heart disease, or infections. It can also help monitor chronic conditions like lupus or rheumatoid arthritis.

How the Test Works

A small blood sample is drawn from your arm. The serum or plasma is then analyzed using a nephelometry method, which measures how much light is scattered by the CRP protein in your blood. This helps determine its concentration.

What to Expect Before the Test

No special preparation is needed, but inform your doctor if you’re taking blood thinners or have a history of bleeding disorders. Avoid strenuous activity 24 hours before the test if your doctor recommends it, as it may affect inflammation levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Nephelometry)

Frequently asked questions

What does a high CRP level mean?
A high CRP level suggests inflammation is present in your body. While it doesn’t pinpoint the exact cause, it can signal infections, autoimmune diseases, or other inflammatory conditions. Your doctor will use the results along with your symptoms and medical history to guide further testing or treatment.
What does a low CRP level mean?
A low CRP level usually means there is little to no inflammation in your body. However, it can also occur in people with very mild or controlled inflammatory conditions. If your CRP is consistently low, your doctor may reassess your treatment plan or monitor for other health issues.
Can CRP levels change over time?
Yes, CRP levels can fluctuate based on your health status, recent infections, injuries, or medications. For example, CRP may spike after surgery or an illness and return to normal as your body heals. Regular monitoring can help track how well your treatment is working for chronic conditions.
  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