Lab values
Therapeutic Drug Levels
Adult reference ranges in US units with the SI equivalent. Ranges differ a little between labs; use your lab’s printed range.
| Test | US units | SI units | Notes |
|---|---|---|---|
| Digoxin | 0.5–2.0 ng/mL | 0.6–2.6 nmol/L | Heart failure often 0.5–0.9; toxicity more likely with low potassium |
| Lithium | 0.8–1.2 mEq/L | 0.8–1.2 mmol/L | Maintenance 0.8–1.0; 1.5 or higher toxicity SI: Maintenance 0.8–1.0; 1.5 mmol/L or higher toxicity |
| Phenytoin | 10–20 mcg/mL | 40–79 µmol/L | |
| Theophylline | 10–20 mcg/mL | 55–110 µmol/L | |
| Vancomycin | AUC 400–600 mg·h/L (MIC 1) | AUC 400–600 mg·h/L (MIC 1) | ASHP/IDSA 2020 for serious MRSA; trough-only targets of 15–20 mcg/mL are older practice |
Study the labs
- ABG Interpretation in 6 StepspH, PaCO₂, HCO₃⁻, compensation, anion gap and oxygenation, with worked examples
- Electrolyte ImbalancesNa, K, Ca, Mg and phos: normals, ECG clues, safe replacement, hyperkalemia steps
- Pediatric Assessment and EmergenciesPAT, vital signs, airway infections, febrile seizures, dehydration, arrest, choking and abuse
- Bleeding, Reversal, HIT and DICAnticoagulant reversal, the 4Ts and HIT care, DIC and TTP for critical care exams
Other lab values
- Chemistry
- Hematology
- Coagulation
- Arterial blood gas
- Liver and pancreas
- Cardiac
- Urine
- Pediatric vital signs by age
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Sources
- MedlinePlus Medical Encyclopedia ranges (National Library of Medicine, reviewed 2024–2026); ABIM laboratory reference ranges (January 2026) for hemoglobin, hematocrit and potassium; Merck Manual for ionized calcium; the heparin label for the aPTT target; ASHP/IDSA 2020 vancomycin guideline
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow the order, the label and your institution's protocols.