Sugars and their polymers are the most abundant molecules on the planet. They are widely known as an energy source, starting with plants using solar energy to produce them to other living organisms consuming those very ones. The same carbohydrate structures are present in cells as skeletal scaffolding and, on a larger scale, as support in plants and trees. However, they also participate in a wide assortment of biochemical processes needed for life – from fertilization to cell apoptosis. Furthermore, they are involved in cell recognition events such as adhesion, communication and invasion by bacteria/viruses, contact inhibition of cell division, triggering of the immune response and more. With carbohydrates taking part in such a wide array of important processes, they have been found useful in intercepting those same processes for therapeutic purposes. Carbohydrate-based antibiotics such as neomycin and gentamicin were first synthesized in the 1940s but are still used today. D-ribose and D-deoxyribose derivatives are used to interrupt the replication processes of pathological cells and viruses. Some effective antidiabetic drugs are conjugates and derivatives of D-glucose. Adriamycin is a chemotherapy drug used in treating cancer. Glycans can also be used in disease diagnostics, e.g. recognizing glycans present on the surface of viruses, bacteria and eukaryotic cells, and recognizing altered glycosylation of cancer cells. At the Department of Organic Chemistry of the University of Debrecen, in the Chemical Glycobiology Research Group, a large number of bioactive monosaccharide derivatives — e.g. C–glycopyranosyl-aromatic and heteroaromatic derivatives as glycoenzyme, glycotransporter and lectin inhibitors with antidiabetic potential — have been designed and synthesized. Furthermore, they have synthesized and patented several sandwich-type platinum-group metal complexes with possible anticancer properties. These complexes have shown significant cytostatic effects against carcinoma, lymphoma and sarcoma cancer cells as well as antibacterial activity against some strains of multiresistant Gram-positive bacteria. Understanding what roles glycans play in disease-inducing processes gives motivation to the development of carbohydrate-based medicine. From the year 2000 to 2021, fifty-four carbohydrate-based compounds have been designed and approved as drugs or diagnostic agents: ranging from antiviral, antibacterial/antiparasitic, anticancer, antidiabetic drugs, as well as cardiovascular drugs, nervous system drugs and others. Such a rapid rate of progress makes the present an exciting and promising era for effective drug design and therapeutic progress.