The purpose of our study was to clarify limitations of off-label use for low cost nonmedical use (NMU) pulse oximeters by primary care providers. These devices are widely marketed over the Internet and in drugstores but are not intended for medical use or reviewed by the Food and Drug Administration (FDA). Our study compared oxygen saturation (SpO ) in patients from 1 medical use (MU) pulse oximeter to 8 NMU pulse oximeters. Measured arterial oxygenation (SaO ) was compared with SpO when available.