Wearable medical systems, which are used for medical monitoring, assessment, and/or treatment have the essential requirements to be low energy consuming and reliable. They must be energy efficient, so that battery size is minimal, to ensure that the systems are convenient to use. Also, they must be highly reliable, because they are being developed for critical medical applications. In this paper we examine the critical requirement of energy minimization, specifically for wearable medical systems. We present an overview of the general power management schemes, along with more specific approaches tailored to wearable systems. We specifically highlight two medical wearable systems, RFAB and CustoMed, being developed by our group. Finally, we discuss the relationship between reliability and power management, and how this impacts the critical medical systems we are examining.