Heat shock proteins (HSPs) are a highly conserved family of proteins that are expressed by all cells exposed to environmental stress and have different functions. They are categorised into 7 main families according to their molecular weight: HSP10 (HSPE); small HSPs with a molecular weight of 12-43 kDa (e.g., HSP27 or HSPB1); HSP40 (DNAJ); HSP60 (HSPD); HSP70 (HSPA); HSP90 (HSPC) and HSP100. As molecular chaperones, they promote the correct folding of proteins under physiological conditions. HSPs are essential for many cellular processes, from regulation of the cell cycle to involvement in the process of apoptosis (vasorelaxation, actin stabilisation, chaperone function, apoptosis survival functions, antioxidant activity, anti-inflammatory activity, etc.). HSPs are associated with the causes of type 1 diabetes and in the treatment of insulin resistance in type 2 diabetes and obesity. Recent studies have shown that HSPs are involved in the pathogenesis of cancer, neurodegenerative diseases, diseases of the circulatory system and in autoimmune diseases and that they are associated with a number of clinical conditions such as diabetes and its consequences (angiopathy, neuropathy, retinopathy, lack of antioxidant defence system and lipid profile disturbance and chronic hyperglycemia). In these diseases, certain HSPs are expressed or suppressed so that they can be used as potential diagnostic and therapeutic targets. This, of course, requires very sensitive and reliable analytical methods for their determination. This review describes the properties of HSPs, their characterisation and structure, their biological functions and the presence and disruption of HSPs in diabetes and secondary complications of diabetes.