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C-reactive protein (serum/plasma concentration)

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

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

Quick summary

["CRP helps doctors assess inflammation, infection risk, or autoimmune activity."]

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

Key facts at a glance

LOINC
22172-1
Short code
C pneum IgG Titr Ser
Synonyms
C pneum IgG Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82977
SNOMED
3110003
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

What Is C-Reactive Protein Used For?

CRP is primarily used to monitor inflammation in conditions like infections, autoimmune diseases (e.g., rheumatoid arthritis), or after surgeries or injuries. It can also help track response to treatments or identify early signs of complications.

When Might You Need This Test?

Your doctor may order CRP if you have symptoms like fever, joint pain, or unexplained swelling, or if you’re at risk for conditions like heart disease, kidney problems, or certain infections. It’s also sometimes checked during routine check-ups or after a diagnosis of inflammation-related illness.

How Is the Test Done?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure CRP levels. Results are typically ready within 24 hours.

What Do My Results Mean?

Higher CRP levels may indicate active inflammation, infection, or an autoimmune response. Lower levels suggest minimal inflammation. Your doctor will interpret results in the context of your symptoms and medical history.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

Why was I asked to fast before this test?
Fasting may be recommended to ensure accurate results, as certain foods or medications can temporarily affect CRP levels. Follow your doctor’s instructions to avoid unnecessary stress on your results.
Can CRP levels change with diet or exercise?
Yes, lifestyle factors like diet, exercise, and stress can influence inflammation. While CRP is a useful marker, it’s not the only factor doctors consider when assessing your health.
Is CRP the same as a white blood cell count test?
No, CRP measures a protein linked to inflammation, while a white blood cell count assesses the number of immune cells in your blood. Both tests serve different purposes in diagnosing conditions.
  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