What Are ACE Inhibitors? ACE, or Angiotensin Converting Enzyme, Inhibitors are a class of medications that your healthcare provider may prescribe to help control high blood pressure or hypertension. High blood pressure is diagnosed by either 1. Systolic blood pressure (the top number of the blood pressure reading) consistently 140 mmHg or higher, or 2. Diastolic blood pressure (the bottom number of the blood pressure reading) consistently 90 mmHg or higher.