Drugs & toxicology

Phenytoin unit converter

Anti-seizure drug level (therapeutic range)

Also known as: Diphenylhydantoin, DPH, Phénytoïne, Fenitoína, Dilantin, Epanutin

Converter

Enter a value in any unit and all other units fill in.

mg/L µmol/L mg/dL µg/dL

Worked example

15 mg/L (middle of the reference range) = 59.5 µmol/L

Conversion formulas

µmol/L	µmol/L = mg/L × 3.964	mg/L = µmol/L × 0.2523
mg/dL	mg/dL = mg/L × 0.1	mg/L = mg/dL × 10
µg/dL	µg/dL = mg/L × 100	mg/L = µg/dL × 0.01

Reference range

Unit	Adults
mg/L	10 – 20
µmol/L	39.64 – 79.28
mg/dL	1 – 2
µg/dL	1000 – 2000

Source: FDA drug label (DailyMed): phenytoin · Last reviewed: 2026-10-14

Note from the source: Clinically effective total serum concentration 10-20 mcg/mL (unbound 1-2 mcg/mL); nystagmus usually from 20 mcg/mL (FDA label)

Frequently asked questions

How do I convert Phenytoin from mg/L to mg/dL?

mg/dL = mg/L × 0.1. In the other direction: mg/L = mg/dL × 10.

What is the reference range of Phenytoin?

For adults the range is 10 – 20 mg/L (FDA drug label (DailyMed): phenytoin). Reference ranges differ between laboratories and partly by sex and age; use the range printed on your lab report.

Which units are used for Phenytoin?

Common units are mg/L, µmol/L, mg/dL, µg/dL.