Low-dose oral methotrexate is associated with wrong frequency dosing errors, when taken once daily instead of the intended once weekly schedule. The Institute for Safe Medication Practices (ISMP) has classified methotrexate (oral, nononcologic use) as a high alert medication that can cause fatal and serious adverse events when mistakenly taken daily. However, the incidence of wrong frequency dosing errors with methotrexate is unknown. A chart confirmed analysis was conducted in one Sentinel Data Partner (Kaiser Permanente Northern California) and found the incidence of low-dose oral methotrexate wrong frequency dosing errors to be 0.4%. FDA used Sentinel findings to revise the methotrexate labeling in 2019, which included adding a new Warnings and Precautions section on the risk of improper dosing, removing an option for doses given every 12 hours for 3 days each week, and recommending that patients and caregivers be instructed to take methotrexate as directed as dosing errors have led to fatal toxicity. In July 2020, ISMP highlighted the labeling revision in their Medication Safety Alert! newsletter.