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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 in your blood, a substance produced by your body in response to inflammation.

Quick summary

["CRP helps doctors assess inflammation, often used to monitor conditions like infections, autoimmune diseases, or heart disease."]

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

Key facts at a glance

LOINC
45092-4
Short code
C trach Ag Nph Ql IA
Synonyms
C trach Ag Nph Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 for inflammation, meaning it signals when your body is fighting an infection, healing from injury, or responding to conditions like arthritis or heart problems. High levels may indicate an active inflammatory process, while low levels suggest reduced inflammation.

What Can Cause Changes in CRP Levels?

CRP can rise due to infections (like pneumonia or urinary tract infections), injuries, surgeries, or certain medications. It may also be elevated in conditions such as rheumatoid arthritis, lupus, or heart disease. Stress, smoking, or obesity can also influence CRP levels.

When Is a CRP Test Ordered?

Doctors may order a CRP test to monitor chronic conditions, check for infections, evaluate heart disease risk, or assess response to treatment for inflammatory diseases. It’s sometimes used alongside other tests to guide treatment decisions.

What Does a High or Low CRP Level Mean?

A high CRP level often signals inflammation, prompting further investigation into possible infections, autoimmune diseases, or other health concerns. A low CRP level may mean inflammation is under control, but it doesn’t rule out all causes of low-grade inflammation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CRP

Frequently asked questions

What are the normal reference ranges for CRP?
CRP reference ranges vary by lab and may differ slightly between serum and plasma. Typically, low levels (often below 1 mg/L) suggest minimal inflammation, while moderate to high levels (above 3–10 mg/L) may warrant further evaluation. Your doctor will interpret results in the context of your symptoms and medical history.
How often should I get a CRP test?
Your doctor will determine how often you need a CRP test based on your health condition, treatment plan, or symptoms. Some people may need it monthly, quarterly, or annually, depending on their situation.
Can lifestyle changes affect CRP levels?
Yes, lifestyle factors like diet, exercise, smoking, and stress can influence CRP levels. Reducing inflammation through a balanced diet, regular physical activity, quitting smoking, and managing stress may help lower CRP levels over time.
  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