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

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

This test measures the level of C-reactive protein in your blood, a marker often used to check for inflammation or infection.

Quick summary

["CRP helps track inflammation, guiding decisions about treatments or further testing."]

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

Key facts at a glance

LOINC
87318-2
Short code
EC eaeA gene Islt Ql NAA+probe
Synonyms
EC eaeA gene Islt Ql NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
5
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
CPT
82378
SNOMED
394995008
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 monitor conditions like infections, autoimmune diseases, or inflammation. It can also help assess risk for heart disease or evaluate response to treatment for conditions such as arthritis or other inflammatory disorders.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Higher-than-normal CRP levels may indicate inflammation, infection, or other health issues. Lower levels suggest reduced inflammation. Your provider will interpret results in the context of your overall health and symptoms.

Common Conditions Monitored

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

Reference range

Non-smokers: <2.5 ng/mL; Smokers: <5.0 ng/mLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP Plasma

Frequently asked questions

What causes CRP levels to be higher than normal?
CRP can rise due to infections (like flu or urinary tract infections), injuries, surgeries, or inflammatory diseases (like arthritis). Stress, certain medications, or pregnancy may also temporarily affect levels.
How often should I get this test?
Your provider will determine how often you need this test based on your health condition and treatment plan. Some people get it every few months, while others may need it less frequently.
Can lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet (e.g., Mediterranean diet), exercise, and avoiding smoking can influence CRP levels. Reducing inflammation may lower CRP, but results depend on overall health and medical 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