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Procalcitonin (PCT)

Published: July 27, 2026Updated: August 25, 2026

Procalcitonin (PCT) is a peptide precursor of calcitonin that increases in response to bacterial infections and sepsis, making it useful for diagnosing and monitoring bacterial infections.

Quick summary

PCT levels help diagnose bacterial infections and sepsis.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
ng/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche PCT Gen, Brahms PCT Sensitive
interpretation: {"text":"0–0.25 ng/mL: Low risk of bacterial infection.","label":"Normal"}; {"text":">0.25 ng/mL: Possible bacterial infection or sepsis, requiring further investigation.","label":"Elevated"}

Procalcitonin (PCT) is a biomarker that is particularly useful in differentiating bacterial infections from viral infections. It is produced in the C cells of the thyroid gland and increases significantly in response to bacterial endotoxins.

In clinical settings, PCT levels are measured to guide antibiotic therapy, as elevated levels can indicate the presence of a bacterial infection. This helps in reducing unnecessary antibiotic use.

The reference range for PCT is typically 0–0.25 ng/mL. Levels above this range may suggest a bacterial infection or sepsis, prompting further diagnostic evaluation and treatment.

Frequently asked questions

What is the role of procalcitonin in diagnosing infections?
Procalcitonin helps differentiate bacterial infections from viral infections and guides antibiotic therapy.
How are procalcitonin levels measured?
Procalcitonin levels are measured through a blood test, with results typically available within a few hours.
  1. 1
    Procalcitonin as a diagnostic marker of sepsis in critically ill patientsSource
  2. 2
    Use of procalcitonin to guide antibiotic therapySource

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 25, 2026. · Read our editorial policy