Blood Test

Procalcitonin (PCT) Test

Name: Procalcitonin Test: Normal Range | HealthReview
Creator: Suman Konda
Published: 2026-07-05

Procalcitonin is a blood test that helps doctors distinguish bacterial from viral infections and diagnose sepsis early. It guides decisions about whether antibiotics are needed: a key tool in reducing antibiotic resistance.

Written and clinically reviewed by Suman Konda, PharmD, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: 01 August 2026 · How we check our content

What is procalcitonin?

Procalcitonin (PCT) is the precursor to the hormone calcitonin (which regulates calcium). In healthy people, PCT levels in the blood are very low. During bacterial infections (especially systemic ones), bacterial toxins and cytokines stimulate PCT production throughout the body: causing levels to rise rapidly within 2-4 hours and peak at 24-48 hours. Viral infections cause only mild or no rise in PCT because viral infections do not trigger the same bacterial-specific immune pathways. This makes PCT the most useful biomarker for distinguishing bacterial from viral infections in clinical practice.

Procalcitonin normal range and interpretation

PCT Level (ng/mL)	Interpretation	Action
< 0.1	Normal	Bacterial infection very unlikely
0.1 – 0.25	Slightly elevated	Localised bacterial infection possible; antibiotic decision individualised
0.25 – 0.5	Moderately elevated	Bacterial infection likely; consider antibiotics
0.5 – 2.0	High	Bacterial infection probable; antibiotics recommended
> 2.0	Very high	Sepsis likely; urgent treatment
> 10	Severely elevated	Severe sepsis / septic shock

Procalcitonin in sepsis

Sepsis is a life-threatening organ dysfunction caused by the body's dysregulated response to infection. Procalcitonin is one of the most useful sepsis biomarkers. High PCT (>2 ng/mL) combined with clinical signs of infection and organ dysfunction supports a sepsis diagnosis. PCT is also used to guide antibiotic de-escalation: a falling PCT (more than 80% reduction from peak) indicates the infection is responding and antibiotics can be stopped sooner, reducing antibiotic resistance and side effects.

Conditions that can cause false elevation

Major surgery or trauma (non-infectious PCT rise)
Severe burns
Prolonged cardiogenic shock
Medullary thyroid cancer (rare source of calcitonin/PCT)
Newborns in the first 48 hours (normal physiological elevation)

Questions to ask your doctor

Is my infection bacterial or viral?
Do I actually need antibiotics based on my PCT level?
Is my PCT falling with treatment?
Can antibiotics be stopped safely now?

Frequently Asked Questions

What does procalcitonin tell doctors?

Procalcitonin rises specifically with bacterial infection, helping distinguish bacterial from viral illness and guiding whether antibiotics are needed, particularly in chest infections and suspected sepsis.

How is it different from CRP?

Both rise with inflammation, but procalcitonin is more specific to bacterial infection, whereas CRP rises with many types of inflammation, so procalcitonin can help refine antibiotic decisions.

Is procalcitonin used to stop antibiotics?

Yes. Falling procalcitonin levels can support safely stopping antibiotics in some hospital settings, helping reduce unnecessary antibiotic use.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

Procalcitonin. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK539794