Stevia and its glycosides are becoming more popular both in the world of science and in the food industry. This review discusses the functional properties of Stevia, which is mainly used as an alternative sweetener. The results of research revealed significant health-promoting properties of Stevia and steviol glycosides applied at certain doses and under specific conditions. Stevia preparations exhibit anti-inflammatory, oral health-promoting, antihypertensive, and chemopreventive effects. Moreover, they help to regulate glycaemia, inter alia, by affecting glucose uptake, improving insulin secretion or increasing the concentration of glucose transporters. Most of the results concerning the antidiabetic properties of Stevia come from in vitro and in vivo studies. So far there have been only a few clinical trials conducted on humans. As the mechanisms underlying these effects have not been fully understood, they require further investigation. This article presents the state of the art concerning this issue.