Skip to content

C-reactive protein (CRP) concentration in serum/plasma

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

This test measures the level of C-reactive protein, a protein your body produces in response to inflammation.

Quick summary

["CRP helps doctors check for inflammation in your body."]

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

Key facts at a glance

LOINC
74148-8
Short code
CFAP
Synonyms
CF action plan
Category
chemistry
Sample
serum
Container
N/A - Clinical document, not a specimen collection test. Documentation typically maintained in electronic health record (EHR) and provided as printed action plan for patient/caregiver use.
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Clinical assessment and care plan documentation; not a quantitative laboratory assay. Based on clinical evaluation, pulmonary function tests, sputum/sweat chloride correlation, and nutritional assessment.
CPT
N/A - Not a separately billable laboratory test. May be incorporated into CF comprehensive evaluation codes (e.g., 99213-99215 for established patient visits).
SNOMED
38341003 | Cystic fibrosis (Disorder) | and related concepts for care planning documentation
Specimen volume
N/A - No specimen required for this clinical care plan document.
Stability
N/A - No specimen required.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to monitor conditions like infections, autoimmune diseases, or inflammation. It can also help assess risk for heart disease or check for signs of tissue damage or injury.

What Does a High or Low Level Mean?

Elevated CRP levels often indicate inflammation, which can be due to infections, injuries, or certain diseases. Lower-than-normal levels may suggest reduced inflammation, but they don’t always mean you’re healthy.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure CRP levels using a sensitive immunoassay method.

What Are Common Uses?

This test is commonly used to track inflammation over time, evaluate symptoms of conditions like rheumatoid arthritis or lupus, and sometimes screen for heart disease risk.

Reference range

N/A - This is a clinical care plan document, not a quantitative laboratory test with numerical reference ranges.N/A

Specimen: serum

No fasting required. Patient should bring current medication list, recent pulmonary function test results, sputum culture results, and any home monitoring data (peak flow, weight, oxygen saturation logs). For pediatric patients, caregiver should accompany and provide feeding/dietary history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CRP is a marker for systemic inflammation. While it doesn’t diagnose specific conditions, it helps guide treatment decisions and monitor responses to therapy. High CRP may prompt further testing for underlying causes, such as infections or autoimmune disorders.

Short name

CRP (Serum/Plasma)

Frequently asked questions

What causes CRP levels to change?
CRP levels can rise due to infections (like colds or flu), injuries, surgeries, or certain medications. They may also be higher in people with chronic conditions like arthritis or heart disease. Stress or recent illness can temporarily increase CRP.
How soon after a trigger (like an infection) might CRP levels return to normal?
CRP levels often return to normal within days to weeks, depending on the cause. For example, after a viral infection, CRP may drop quickly, but in chronic conditions, it may stay elevated longer.
Can CRP levels be affected by diet or lifestyle?
Diet and lifestyle factors like smoking, exercise, and weight can influence inflammation levels, which may indirectly affect CRP. However, CRP itself is not directly affected by diet alone.
  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