Procalcitonin (PCT) in Serum/Plasma
This test measures procalcitonin, a precursor protein made by cells in response to infection, helping assess whether a bacterial infection is present.
["Procalcitonin helps guide decisions about antibiotics and infection management."]
Key facts at a glance
- LOINC
- 19780-6
- Short code
- Proc desc Endscpy
- Synonyms
- Proc desc Endscpy
- Category
- coagulation
- 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 differentiate between bacterial and viral infections. Elevated levels may suggest a bacterial infection, such as pneumonia, sepsis, or other serious illnesses, while lower levels are more typical in viral infections like the flu. Your doctor may order this test if you have symptoms of infection or if you’re at risk for severe illness.
How Is the Test Performed?
A blood sample is drawn from a vein in your arm. The blood is then processed to separate serum or plasma, which is sent to a lab for analysis using an immunoassay method to measure procalcitonin levels.
What Are Common Causes of Elevated Procalcitonin?
High procalcitonin levels can occur in conditions like bacterial infections (e.g., pneumonia, sepsis), inflammatory diseases, or certain types of cancer. It’s not typically elevated in viral infections or stress-related conditions.
What Are Common Causes of Low or Normal Procalcitonin?
Low or normal procalcitonin levels are common in viral infections (e.g., COVID-19, flu), non-infectious inflammatory conditions, or when the body is responding to non-bacterial causes of illness.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Procalcitonin is a useful biomarker for monitoring bacterial infections, especially in critically ill patients or those with unclear sources of infection. It can help doctors decide when to start or stop antibiotics, reduce unnecessary treatments, and improve patient outcomes. However, it’s not a definitive test on its own and should be interpreted alongside clinical findings and other tests.
Short name
PCT (Serum/Plasma)
Frequently asked questions
Why might my doctor order a procalcitonin test?
What do my procalcitonin results mean?
Can procalcitonin levels change over time?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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