Phenytoin (Dilantin)

Tube Type = Blue Top or Red Bullet

No Gel in Red Top Bullet

Tube Type

Test ID   LAB31
EPIC Order
   PHENYTOIN LEVEL, TOTAL
CPT Code(s)   80185
Group/Individual Test   Individual
Laboratory   Core Laboratory
Tube Station   Routine: 30; STAT: 888
Specimen Routine: 3 mL blood/navy blue plain tube/red plain tube also acceptable; See Comments 
  Micro: 300 µL blood/red top pediatric bullet; See Comments
Stability
Unspun - 4 hrs
Spun and Separated Room Temp - 24 hrs
Spun and Separated Refrigerated - 2 days
Spun and Separated Frozen - 5 months
Availability 24 hrs/day
Turnaround Time   STAT: 1 hr; Routine: 2 hrs
Reference Range Therapeutic: 10-20 mcg/mL (Trough, Steady state)
  Toxic: >30 mcg/mL
Comments
  • Red top tubes must NOT contain Serum Separator Gel
  • Collection information: For oral dose, collect as trough immediately before next dose.

Reviewed by J. Carr on January 09, 2026

UNC Hospitals
McLendon Clinical Laboratories
101 Manning Drive
Chapel Hill, NC 27514