Many of the medications that clinicians prescribe to prevent or treat disease can result in unanticipated and unintended toxic effects. Many national clinical guidelines recommend baseline and periodic laboratory monitoring to avoid adverse drug events. Our Safety in Prescribing project (SIP) has found many significant gaps in medication safety. Lab Alert will evaluate electronic tools to improve Kaiser Permanente's performance in laboratory monitoring to avoid adverse drug events. We will enroll patients who are taking high-risk medications and who have not received laboratory monitoring. The primary outcome of this 2-year study is the proportion of patients who receive guideline-based laboratory monitoring at 1 and 3 weeks post-intervention.