Diabetes mellitus is a group of chronic metabolic disorders. Hyperglycaemia and other related disturbances in the body's metabolism can result in serious damage to many of the body's systems, especially the blood vessels and nerves. Across the globe, there are an estimated 150 million people suffering from diabetes mellitus, which causes about 5 % of all deaths globally each year. From many reports it is clear that diabetes will be one of the major diseases in the coming years. Existing treatment options are costly, and have limited palliative effects. It stimulates finding new medicines or suitable prophylactic treatments. Plant-based medicinal products known since ancient times have been used to control diabetes in the traditional medicinal systems. Numerous medicinal plants have been studied and validated for their hypoglycaemic properties using diabetic animal models but not so often in clinical studies. Testing of many plant extracts and plant substances continue. This review paper presents selected information on the hypoglycemic and antihyperglycaemic activities of tested preparations of plant origin.