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

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

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

Quick summary

["CRP helps identify 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
2031-3
Short code
COHgb MFr BldC
Synonyms
COHgb MFr BldC
Category
hematology
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
12
Ref high
17.5
Critical range
7 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85018
SNOMED
900000000000003004
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order a CRP test to check for signs of inflammation, monitor chronic conditions like rheumatoid arthritis or lupus, or evaluate symptoms such as fever, joint pain, or unexplained fatigue. It can also help assess risk for heart disease or guide treatment decisions for infections or injuries.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, which usually causes only mild discomfort. If you’re on blood-thinning medication, let your doctor know before the test.

What the Results Mean

Results are not given as a single number but as a range or comparison to your baseline. Higher levels may indicate active inflammation, while lower levels suggest reduced inflammation. Your doctor will interpret results in the context of your health history and other tests.

Common Conditions Monitored

CRP is used to track inflammation in conditions like infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis, lupus), heart disease, or after surgeries or trauma.

Reference range

Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A

Specimen: whole-blood

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

CRP (Serum/Plasma)

Frequently asked questions

What causes elevated CRP levels?
Elevated CRP levels can be caused by infections (bacterial or viral), autoimmune diseases, heart disease, injuries, or certain medications. Chronic conditions like arthritis or inflammatory bowel disease may also lead to consistently higher CRP levels. Your doctor will consider your symptoms and other test results to determine the cause.
Can CRP levels change over time?
Yes, CRP levels can fluctuate depending on your health status. For example, they may rise after an infection or injury and return to normal as your body heals. Regular monitoring can help track how well treatments are working for conditions like arthritis or heart disease.
Is CRP the same as ESR?
No, CRP and erythrocyte sedimentation rate (ESR) are different tests. CRP measures protein levels in response to inflammation, while ESR measures how fast red blood cells settle in a tube. Both are used to assess inflammation but provide slightly different information.
  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