The effect of medication errors on patient quality care and safety is a critical ongoing concern requiring solutions. Although medication safety has been a concern of all healthcare professions, registered nurses play an important role in medication safety as patients' advocates. A cross sectional study with structured questionnaire on common FDI found in the medical journal was used in this study. The questionnaire consisted of 37 questions (dichotomous and multiple choice questions). A convenience sample of 271 nurses from different inpatient community nursing units (60 medical surgical, 60 telemetry, 29 Intensive care (ICU), 21 emergency, and 101 "others") across the DC-MD-VA metropolitan areas were recruited for this study. The data was subjected to descriptive analysis. The study protocol was approved by the Office of Regulatory, Research Compliance, Howard University. The result, showed no significant differences in the knowledge of FDI among the 5 groups of registered nurses. The authors propose continuing education for all nurses to update dosage calculation, follow drug administration protocol and enhance knowledge of pharmacology as avenues to reduce medication error. The authors also recommend that future studies focus on a larger sample size, inclusion of more associated FDI variables and use of high level statistical analysis.