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Procalcitonin (PCT) in Serum/Plasma

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

This test measures the level of procalcitonin, a protein produced by cells in response to bacterial infections. It helps doctors assess whether an infection is likely caused by bacteria.

Quick summary

["Procalcitonin helps guide treatment decisions for infections, especially in cases where bacteria may be involved."]

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

Key facts at a glance

LOINC
25575-2
Short code
C peptide sp2 p chal SerPl-sCnc
Synonyms
C peptide sp2 p chal SerPl-sCnc
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
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

What Is Procalcitonin Used For?

Procalcitonin is primarily used to distinguish between bacterial and viral infections. Higher levels often suggest bacterial infection, which may require different treatments (such as antibiotics) compared to viral infections.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum or plasma, which is sent to a lab for testing using a sensitive immunoassay method to detect procalcitonin levels.

When Might You Need This Test?

Your doctor may order this test if you have symptoms of infection (such as fever, chills, or cough), if you’re recovering from surgery, or if you have conditions that increase your risk of bacterial infections (like chronic lung disease or sepsis).

What Are Possible Results?

Results are not given in a single range but are interpreted in the context of your symptoms, medical history, and other tests. Low levels may suggest a viral infection, while higher levels could indicate a bacterial infection or other inflammatory conditions.

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

PCT

Frequently asked questions

Why was this test ordered?
Your doctor may have ordered this test to help determine the cause of your symptoms, guide treatment decisions (such as whether antibiotics are needed), or monitor your response to treatment, especially in cases like sepsis or pneumonia.
What do my results mean?
Procalcitonin results alone don’t provide a definitive diagnosis. They are used alongside other tests and clinical findings to help narrow down the likely cause of your infection. Your doctor will discuss the results with you in detail.
Can I avoid this test?
While you can’t always avoid tests, your doctor may choose to order this test based on your symptoms, medical history, or risk factors. If you have concerns, discuss them with your healthcare provider to understand why the test was recommended.
  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