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Procalcitonin (PCT)
A marker of systemic bacterial infection and sepsis. Helps distinguish bacterial from viral inflammation.
Other names: Procalcitonin, PCTSection: Blood chemistry
Updated: August 31, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortProcalcitonin is nearly absent from blood in health but rises with bacterial infection in proportion to severity. Viral infections usually leave it low. The test is used mainly in hospitals to diagnose sepsis and to guide antibiotic decisions.
Reference ranges
Group
Reference range
Outside bacterial infection — typical range (international reference, not a national standard)
low level; exact cutoffs depend on the assay
MedlinePlus describes the test qualitatively: results are read against the assay's thresholds together with the clinical picture. No single standard range applies. Reference ranges vary between laboratories and assays — use the range printed on your own lab report.
Check your value
Enter your result — we will show how it compares with a typical range. Match the units of the selected row.
Approximate comparison with a typical range, not a diagnosis. Reference intervals vary by laboratory and method — check your report; result interpretation is done by a doctor.
What this marker is
PCT is the precursor of the hormone calcitonin. In bacterial infection many tissues release it, and the level tracks the severity of the systemic response; it falls quickly with effective treatment.
Clinicians use PCT to support decisions about starting and stopping antibiotics — for example in pneumonia — always together with the clinical picture.
When it is high
SepsisA marked elevation signals systemic bacterial infection — an emergency.
Bacterial infectionsPneumonia, pyelonephritis, and meningitis raise the level; the trend reflects treatment effect.
Major trauma and burnsMassive tissue damage can elevate PCT without infection.
When it is low
Viral infection or localized processA low level makes systemic bacterial infection unlikely.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Major trauma and burnsRecent extensive surgeryKidney function
How to prepare
No special preparation; the test is performed for clinical indications, usually in hospital.
When a retest makes sense
In hospital — by clinical need, often daily or every other day to follow the trend.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; an infectious disease specialist or intensivist in hospital. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: ProcalcitoninPCT
Units and conversion
Measured in: ng/mL
ng/mL=µg/L
1 ng/mL = 1 µg/L — the number stays the same. Results are rounded to 2 decimal places.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
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