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

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

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

Quick summary

["CRP helps doctors assess inflammation, often used to monitor conditions like infections, autoimmune diseases, or heart disease."]

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

Key facts at a glance

LOINC
20566-6
Short code
CATHTIP
Synonyms
CC # Cath Tip Cult
Category
chemistry
Sample
serum
Container
Sterile, leak-proof container (capped sterile tube or cup) without preservative; do not use formalin or other fixatives
Units
N/A
Ref low
0
Ref high
14
Critical range
— – 15 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
culture
CPT
87088
SNOMED
103132007
Specimen volume
Distal 5 cm of catheter tip (approximately 2-3 cm rolled segment or vortexed in 1-2 mL broth)
Stability
Process immediately or refrigerate at 2-8°C; stable for up to 2 hours at room temperature or 24 hours refrigerated; do not freeze
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

Why Is CRP Tested?

Your doctor may order a CRP test to check for signs of inflammation, monitor chronic conditions, or evaluate symptoms like fever, joint pain, or unexplained fatigue. It can also help guide treatment decisions for conditions like arthritis, heart disease, or infections.

What Does a CRP Test Tell You?

Higher CRP levels may indicate inflammation, infections, or inflammatory diseases. However, CRP alone doesn’t diagnose a specific condition—it’s often used alongside other tests and symptoms to guide further evaluation.

How Is the CRP Test Done?

A blood sample is drawn from a vein in your arm. The sample is sent to a lab, where it’s analyzed to measure CRP levels. Results are typically available within a few days.

What Are Common CRP Test Results?

Results are reported in milligrams per liter (mg/L) or micrograms per milliliter (µg/mL). Interpretation depends on your overall health, symptoms, and medical history. Low levels may suggest no significant inflammation, while elevated levels may warrant further investigation.

Reference range

Negative or no growth (<15 colony-forming units per catheter segment using Maki technique). Growth ≥15 CFU/segment by semi-quantitative culture (Maki) suggests catheter-related bloodstream infection.N/A

Specimen: serum

No special patient preparation required. The catheter tip should be collected aseptically after catheter removal. Disinfect the skin around the catheter insertion site before removal to avoid contamination. Send the distal 5 cm segment of the catheter tip to the laboratory immediately in a sterile container.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CRP plays a key role in identifying and monitoring inflammation. It’s a useful marker for conditions like rheumatoid arthritis, sepsis, or cardiovascular risks, but it’s not definitive on its own. Doctors use it to track disease activity, response to treatment, or risk of complications.

Short name

CRP (Serum/Plasma)

Frequently asked questions

What triggers elevated CRP levels?
Elevated CRP levels can be caused by infections (like pneumonia or urinary tract infections), injuries, autoimmune diseases (like lupus or rheumatoid arthritis), heart disease, or other inflammatory conditions. Stress, smoking, or certain medications may also affect CRP levels.
How long does it take to return to normal?
The time it takes for CRP to return to normal depends on the underlying cause. For infections, it may drop within days to weeks. For chronic conditions like arthritis, CRP levels can fluctuate with treatment and activity of the disease.
Can CRP levels be affected by diet or lifestyle?
Yes, diet and lifestyle can influence CRP levels. Reducing inflammation-promoting foods (like processed foods or sugars), increasing omega-3 fatty acids (found in fish), and staying physically active may help lower CRP levels over time.
  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