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C-reactive protein (CRP) concentration, mass concentration

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

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

Quick summary

["CRP helps doctors assess inflammation, track infections, or evaluate conditions like autoimmune diseases."]

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

Key facts at a glance

LOINC
9929-1
Short code
Q wave Dpth L-II
Synonyms
Q wave Dpth L-II
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
ekg
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 It’s Done

Your doctor may order a CRP test to monitor symptoms of inflammation, check for infections, or evaluate conditions like arthritis, heart disease, or other autoimmune disorders. It can also help guide treatment decisions or track how well you’re responding to treatment.

What to Expect

A small needle will be used to draw blood from a vein in your arm. The process is quick and usually causes only minor discomfort. You may feel a slight pinch, but it won’t take long. No special preparation is needed unless your doctor instructs otherwise.

Possible Results

Results are reported in milligrams per liter (mg/L). Higher levels may indicate inflammation, infection, or other health issues, while lower levels suggest minimal or no inflammation. Your doctor will interpret the results in the context of your overall health and symptoms.

Common Conditions Monitored

CRP is often used to monitor conditions like rheumatoid arthritis, lupus, heart disease, or infections such as pneumonia or sepsis. It can also help detect early signs of inflammation in other chronic diseases.

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.

Clinical Significance

Short name

CRP

Frequently asked questions

How often will I need this test?
The frequency depends on your health condition and treatment plan. Your doctor may recommend it regularly if you have a chronic illness or if you’re undergoing treatment for inflammation or infection. For example, people with rheumatoid arthritis might get CRP tests every few months to check how their treatment is working.
What do my results mean if they’re very high or very low?
Very high CRP levels may signal severe inflammation, infection, or an autoimmune condition. Very low levels might mean there’s little to no inflammation, but they can also indicate certain medical conditions or medications that suppress inflammation. Your doctor will discuss these findings with you based on your medical history and symptoms.
Can I affect my CRP levels with lifestyle changes?
Yes! Lifestyle factors like diet, exercise, and stress management can influence inflammation. Eating a balanced diet, staying active, and reducing stress may help lower CRP levels over time. However, results can vary, and your doctor should guide you on how to interpret any changes.
  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