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Procalcitonin (PCT) in Serum/Plasma

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

This test measures procalcitonin, a precursor protein made by cells in response to infections or inflammation. It helps doctors assess whether a bacterial infection is present.

Quick summary

["Procalcitonin helps guide antibiotic use and infection management."]

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

Key facts at a glance

LOINC
13032-8
Short code
C peptide sp2 p chal SerPl-mCnc
Synonyms
C peptide sp2 p chal SerPl-mCnc
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 viral and bacterial infections. Higher levels often suggest a bacterial infection, which can help guide treatment decisions, such as whether antibiotics are needed.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum or plasma, where the procalcitonin levels are measured using a sensitive immunoassay technique.

When Might You Need This Test?

Your doctor may order this test if you have symptoms of infection (e.g., fever, chills), are recovering from surgery, or have conditions that increase infection risk (e.g., chronic illnesses, weakened immune system). It can also be used to monitor treatment progress in certain cases.

What Does a High or Low Level Mean?

Elevated procalcitonin levels may indicate a bacterial infection, sepsis, or severe inflammation. Lower levels are more typical in viral infections or when the body is not responding to bacterial pathogens. However, results should always be interpreted by a healthcare provider in the context of your overall health and symptoms.

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

Why might my doctor order a procalcitonin test if I have a fever?
Your doctor may use procalcitonin to help determine if your fever is due to a bacterial infection (which may require antibiotics) or a viral infection (which often doesn’t need antibiotics). It’s a tool to support treatment decisions.
Can procalcitonin levels change over time during treatment?
Yes, procalcitonin levels can drop when an infection is treated or resolved. Your doctor may repeat the test to monitor how your body responds to treatment and adjust care as needed.
Is there any risk or discomfort with this blood test?
The blood draw itself is minor and typically causes only mild discomfort. Most people feel fine afterward. Rarely, there may be slight bruising or swelling at the site, but these are usually temporary.
  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