All tests · Therapeutic Drug Levels
Therapeutic Drug Levels
Normal range 10–20 µg/mL (40–79 µmol/L SI). Specimen: Serum (trough).
Also known as: Dilantin level.
| Specimen | Serum (trough) |
|---|---|
| Conventional range | 10–20 µg/mL |
| SI range | 40–79 µmol/L |
| Conversion factor | ×3.96 (conventional → SI) |
| Critical value | > 20 µg/mL (nystagmus, ataxia); > 30 confusion |
| Panel | Therapeutic Drug Levels |
Convert any Phenytoin Level result between units on the unit converter.
The standard teaching reference range for Phenytoin Level is 10–20 µg/mL in conventional units, or 40–79 µmol/L in SI units. This value is measured in serum (trough).
A commonly taught critical (panic) value is > 20 µg/mL (nystagmus, ataxia); > 30 confusion. Critical results are reported to the provider immediately under your facility's policy.
Source: Adult reference values compiled from Pagana & Pagana, Mosby's Diagnostic and Laboratory Test Reference, and Fischbach & Dunning, A Manual of Laboratory and Diagnostic Tests. Reference ranges vary by laboratory, method, age, sex, and population — always use the range printed on the actual result.
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