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Procalcitonin (PCT) in Serum/Plasma

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

This test measures a protein produced by cells in response to infections, helping doctors assess whether a bacterial infection is present.

Quick summary

["PCT helps guide treatment decisions for infections, especially in serious cases like sepsis or pneumonia."]

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

Key facts at a glance

LOINC
25572-9
Short code
C peptide sp14 p chal SerPl-sCnc
Synonyms
C peptide sp14 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 (PCT) is primarily used to distinguish between bacterial and viral infections. In bacterial infections, such as pneumonia or sepsis, PCT levels tend to rise significantly. This can help healthcare providers decide if antibiotics are needed and monitor response to treatment.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm, and sent to a lab. The lab uses a sensitive immunoassay method to measure the amount of procalcitonin in your serum or plasma.

Why Might Your Doctor Order This Test?

Your doctor may order a PCT test if you have symptoms of infection, such as fever, chills, or flu-like illness, especially if they suspect a bacterial infection. It can also be used in critical care settings to monitor patients with suspected sepsis or severe respiratory infections.

What Are Common Causes of Elevated PCT Levels?

Elevated PCT levels are most commonly seen in bacterial infections, including pneumonia, sepsis, and other serious illnesses. It can also rise in response to severe trauma, burns, or certain 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.

◆Associated findings1

Short name

PCT

Frequently asked questions

What does a high PCT level mean?
A high PCT level suggests your body is responding to a likely bacterial infection. This can help doctors determine if antibiotics are needed and how to manage your care.
What does a low or normal PCT level mean?
A low or normal PCT level means your body is less likely responding to a bacterial infection, which may help doctors rule out bacterial causes of your symptoms and focus on other treatments.
Can PCT levels change over time?
Yes, PCT levels can change as your infection or condition improves or worsens. Your doctor may retest PCT levels to monitor progress and adjust treatment as needed.
  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