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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 risk."]

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

Key facts at a glance

LOINC
6370-1
Short code
Cryptoc Ab Ser Ql IF
Synonyms
Cryptoc Ab Ser Ql IF
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
85610
SNOMED
396252006
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 Matters in Your Health

CRP is a marker that signals your body’s immune response. It rises when tissues are damaged or when infections, injuries, or inflammatory conditions (like arthritis) are present. While CRP itself isn’t a direct cause of illness, it helps track how your body is responding to these triggers.

When This Test Is Ordered

Doctors may order CRP tests to check for infections (e.g., pneumonia, urinary tract infections), evaluate autoimmune diseases (e.g., rheumatoid arthritis), assess heart health before procedures, or monitor chronic conditions like lupus or inflammatory bowel disease. It’s also used in some screening for cardiovascular risks.

How the Test Works

Blood is drawn and sent to a lab where it’s analyzed using an immunoassay method. This detects CRP levels by measuring how it binds to antibodies. The result is expressed in milligrams per liter (mg/L) or micrograms per milliliter (µg/mL), though exact reference ranges vary by lab.

What Your Results Mean

Results are interpreted based on your symptoms, medical history, and other tests. Elevated CRP (above normal levels) suggests inflammation, while low or normal levels may indicate no active inflammation. Your doctor will discuss findings in the context of your overall health.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP (Serum/Plasma)

Frequently asked questions

What does a high CRP level mean?
A high CRP level often signals inflammation, which can be caused by infections, injuries, or autoimmune diseases. It’s not a definitive diagnosis but a clue that your body is fighting something. For example, very high CRP might prompt further testing for conditions like sepsis or severe arthritis.
Can CRP levels change over time?
Yes, CRP levels can fluctuate. They may rise after infections, surgeries, or even minor illnesses like colds. Some chronic conditions (like heart disease or lupus) also cause steady, lower-level CRP. Your doctor may retest CRP periodically to track changes.
Is CRP the same as a white blood cell count?
No, CRP is different. CRP is a protein produced by the liver in response to inflammation, while white blood cell counts measure the number of immune cells in your blood. Both can be useful, but they serve different purposes—CRP focuses on inflammation, while white blood cells track immune activity.
  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