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Procalcitonin (PCT) concentration in serum/plasma

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

This test measures procalcitonin, a precursor protein made by cells in response to bacterial infections. It helps distinguish between bacterial and viral illnesses.

Quick summary

["Procalcitonin helps guide decisions about antibiotics when infections are suspected."]

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

Key facts at a glance

LOINC
19779-8
Short code
Proc Endscpy
Synonyms
Proc Endscpy
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
endoscopy
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 assess whether a fever or infection is caused by bacteria (which raises PCT levels) or by viruses (which typically do not). Doctors may order this test if you have symptoms like fever, chills, or signs of infection, especially if antibiotics are being considered.

When Might You Need This Test?

You might need a procalcitonin test if you have symptoms of infection, such as fever, sore throat, or flu-like illness. It’s also used in hospital settings to monitor people with severe infections, like pneumonia or sepsis, to decide if antibiotics are needed.

How Is the Test Done?

A blood sample is taken from a vein in your arm. The blood is then processed to measure the procalcitonin levels in your serum or plasma.

What Do Results Mean?

Higher than normal levels of procalcitonin often suggest a bacterial infection. Lower levels may indicate a viral infection or no serious bacterial infection. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

PCT

Frequently asked questions

Why do doctors sometimes order a procalcitonin test even if I don’t have a clear infection?
Doctors may order it to help decide if antibiotics are needed for symptoms like fever or flu-like illness, especially if other tests are unclear. It can also help track how well a treatment is working in people with ongoing infections.
Can procalcitonin levels change over time?
Yes, procalcitonin levels can rise quickly during bacterial infections and may drop as the infection improves or treatments work. Your doctor will monitor changes over time to guide care.
Is this test always done in a hospital?
No, it can be done in hospitals, clinics, or even some doctor’s offices. Blood tests like this are common in outpatient settings for routine or follow-up care.
  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