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C-reactive protein (CRP) in serum/plasma (high-sensitivity)

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

This test measures a protein produced by the liver in response to inflammation, often used to monitor or screen for conditions like infections, autoimmune diseases, or cardiovascular risk.

Quick summary

["High CRP levels may signal inflammation, helping doctors track health conditions or guide treatment decisions."]

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

Key facts at a glance

LOINC
21156-5
Short code
Deprecated CD14 Cells Fr XXX
Synonyms
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Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is This Test Done?

Healthcare providers may order hs-CRP to assess general inflammation, evaluate risk for heart disease, or monitor chronic conditions like rheumatoid arthritis or lupus. It’s sometimes used in screening for infections or after surgery to check for signs of complications.

What Does the Result Mean?

Results are not provided as a single reference range—interpretation depends on clinical context. Elevated levels may indicate inflammation, while lower levels suggest reduced inflammation. Your doctor will discuss findings in relation to your symptoms and medical history.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed using a sensitive immunoassay method to detect CRP levels accurately.

What Are Common Causes of Abnormal Results?

Elevated CRP can result from infections (e.g., pneumonia, urinary tract infections), autoimmune diseases (e.g., rheumatoid arthritis), injuries, or certain medications. Low CRP may occur with chronic stable conditions or in people with very low inflammation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

hs-CRP

Frequently asked questions

Why might my doctor order this test if I don’t have obvious symptoms of inflammation?
Your doctor may use hs-CRP to assess general health risks, monitor chronic conditions, or evaluate for subtle inflammation that could affect your heart health or other organs, even when you feel well.
Can I influence my CRP levels without changing medications?
Yes! Lifestyle factors like diet (e.g., reducing processed foods), exercise, stress management, and smoking cessation can help lower inflammation and CRP levels over time.
What if my CRP level is in the middle of the range?
A middle-range result doesn’t mean you’re perfectly healthy—it simply means your inflammation isn’t extremely high or low. Your doctor will consider your overall health picture and may recommend further testing or lifestyle adjustments.
  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