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C-reactive protein (CRP) - Quantitative

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

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

Quick summary

["CRP helps identify inflammation, often linked to infections, injuries, or autoimmune conditions."]

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

Key facts at a glance

LOINC
71511-0
Short code
ISOLATIONSTATIONS
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
esrd
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 CRP is Tested

Doctors may order a CRP test to check for signs of inflammation, monitor chronic conditions like arthritis or heart disease, or evaluate symptoms such as fever, pain, or swelling. It can also help assess how well treatments are working for conditions like infections or autoimmune diseases.

What to Expect Before the Test

You can eat and drink normally before the test. Bring any medications you’re currently taking. Avoid strenuous activity the day before, as it might affect your results.

During the Test

A healthcare professional will insert a small needle into a vein in your arm to draw a blood sample. You may feel a slight pinch or prick, but it usually doesn’t cause discomfort. The process takes a few minutes.

After the Test

You can resume your normal activities immediately. Apply gentle pressure to the site to stop any bleeding, and check for any unusual swelling or bruising. Avoid heavy lifting or strenuous exercise for a few hours.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What does a high CRP level mean?
A high CRP level suggests inflammation is present in your body. This could be due to infections (like pneumonia or urinary tract infections), injuries, autoimmune diseases (like rheumatoid arthritis), or other inflammatory conditions. Your doctor will use the results along with other tests and symptoms to determine the cause.
What does a low CRP level mean?
A low CRP level typically means there is little to no inflammation detected in your blood. However, it doesn’t rule out other conditions that may not cause inflammation. If you have symptoms like pain, fever, or swelling, further testing may still be needed to find the cause.
Can CRP levels change over time?
Yes, CRP levels can change depending on your health status, recent infections, medications, or other factors like stress or exercise. If your doctor orders repeated CRP tests, results may vary, so it’s important to discuss any changes with them.
  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