To download Critical Values for Therapeutic Drug Levels, click here.
The concept of critical values for drug levels was originally developed by the late Daniel M. Baer, MD, and first published in the April 1982 issue of MLO. This table was reviewed by Rajasri Chandra, MS, MBA and lists the critical values for common therapeutic drugs updated in 2025 by reputed laboratories in the United States. Ranges are approximate and may vary by laboratory and/or assay. Proper interpretation of therapeutic drug concentrations requires that the specimen be drawn at an appropriate time in relation to drug administration.
Critical values for therapeutic drugs are drug levels in a patient’s body that are dangerously high or low, potentially leading to serious or life-threatening effects. These values fall outside the therapeutic ranges and often require immediate clinical attention.
The purpose of monitoring is as follows:
- Efficacy (drug is at a high enough level to be effective)
- Safety (not so high that it becomes toxic)
