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C-reactive protein (CRP) in 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 after surgery.

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

Key facts at a glance

LOINC
80681-0
Short code
C parvum+hominis COWP Stl Ql NAA+probe
Synonyms
C parvum+hominis COWP Stl Ql NAA+probe
Category
coagulation
Sample
stool
Container
Clean container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why CRP Matters in Your Health

CRP is a marker that signals your body’s immune response. It rises when tissues are damaged or when infections or autoimmune conditions are active. While CRP itself isn’t the cause of illness, it helps doctors track how your body is responding to treatment or identify new problems early.

Common Uses for CRP Testing

Doctors may order CRP tests to check for infections (like pneumonia or urinary tract infections), evaluate autoimmune diseases (such as rheumatoid arthritis), monitor heart disease risk, or assess healing after surgery or injury. It can also help guide decisions about starting or stopping certain medications.

How the Test Works

Your blood is drawn, and the CRP level is measured using an immunoassay method. This test detects the protein in your blood and provides a quantitative result to help your healthcare provider interpret your health status.

What to Expect Before the Test

No special preparation is needed for most CRP tests. However, if your doctor has specific instructions—for example, avoiding certain foods or activities—they will let you know. For some tests, fasting may be recommended, but this is less common for CRP.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated CRP levels often indicate inflammation, which can signal infections, injuries, or chronic conditions like arthritis or heart disease. While a single high result doesn’t always mean a serious problem, repeated or consistently elevated levels may prompt further investigation. Low or normal CRP levels suggest minimal inflammation, but they don’t rule out all causes of illness.

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 an infection, an autoimmune condition, or other factors like trauma, surgery, or certain medications. Your doctor will use the result along with other tests and symptoms to determine the cause and next steps.
Can CRP levels change over time?
Yes, CRP levels can fluctuate. They may rise quickly in response to acute infections or injuries and then return to normal as your body heals. Chronic conditions like arthritis or heart disease may also cause CRP levels to stay elevated over time. Your doctor will track changes to understand your health better.
Is CRP testing painful or uncomfortable?
The blood draw for CRP testing is typically quick and may cause a slight pinch or discomfort. Most people find it similar to having a routine blood test. Afterward, you may experience a small bruise or swelling at the site, but this usually goes away within a few days.
  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