| Test | Conventional | SI | Threshold |
|---|---|---|---|
| Acetaminophen Level | 10-30 (therapeutic) µg/mL | 66-199 µmol/L | > 150 µg/mL at 4 h post-ingestion risks hepatotoxicity |
| Carbamazepine Level | 4-12 µg/mL | 17-51 µmol/L | > 12-15 µg/mL (ataxia, diplopia, drowsiness) |
| Digoxin Level | 0.8-2 ng/mL | 1-2.6 nmol/L | > 2.0 ng/mL is toxic (many target 0.5-0.9 in heart failure) |
| Lithium Level | 0.6-1.2 mEq/L | 0.6-1.2 mmol/L | > 1.5 mEq/L is toxic; > 2.0 is a medical emergency |
| Phenytoin Level | 10-20 µg/mL | 40-79 µmol/L | > 20 µg/mL (nystagmus, ataxia); > 30 confusion |
| Salicylate Level | 15-30 (anti-inflammatory) mg/dL | 1.1-2.2 mmol/L | > 40-50 mg/dL (tinnitus, tachypnea, acid-base disturbance) |
| Theophylline Level | 10-20 µg/mL | 56-111 µmol/L | > 20 µg/mL (nausea, tachycardia, seizures) |
| Valproic Acid Level | 50-100 µg/mL | 347-693 µmol/L | > 100-150 µg/mL (sedation, tremor) |
| Vancomycin Trough | 10-20 µg/mL | 7-14 µmol/L | > 20 µg/mL raises nephrotoxicity risk |
Panel
Therapeutic Drug Levels
Digoxin, lithium, phenytoin, vancomycin, and other drugs with narrow therapeutic windows. 9 tests, 9 with a taught threshold.
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Frequently asked questions
What tests are in a Therapeutic Drug Levels?
The Therapeutic Drug Levels on this page lists 9 tests: Acetaminophen Level, Carbamazepine Level, Digoxin Level, Lithium Level, Phenytoin Level, Salicylate Level, Theophylline Level, Valproic Acid Level, Vancomycin Trough. Each is shown with its conventional and SI teaching reference range.
What does the Therapeutic Drug Levels check for?
Digoxin, lithium, phenytoin, vancomycin, and other drugs with narrow therapeutic windows. These are educational teaching values - ranges vary by laboratory and method, and are not for clinical decisions.
Which Therapeutic Drug Levels values are critical?
9 of the 9 tests in this Therapeutic Drug Levels carry a taught threshold: Acetaminophen Level (> 150 µg/mL at 4 h post-ingestion risks hepatotoxicity); Carbamazepine Level (> 12-15 µg/mL (ataxia, diplopia, drowsiness)); Digoxin Level (> 2.0 ng/mL is toxic (many target 0.5-0.9 in heart failure)); Lithium Level (> 1.5 mEq/L is toxic; > 2.0 is a medical emergency); Phenytoin Level (> 20 µg/mL (nystagmus, ataxia); > 30 confusion); Salicylate Level (> 40-50 mg/dL (tinnitus, tachypnea, acid-base disturbance)); Theophylline Level (> 20 µg/mL (nausea, tachycardia, seizures)); Valproic Acid Level (> 100-150 µg/mL (sedation, tremor)); Vancomycin Trough (> 20 µg/mL raises nephrotoxicity risk). These are teaching thresholds, not clinical cutoffs - always use the values your laboratory reports.