Diabetes mellitus (DM) has progressively increased in global prevalence. Recent studies have found that patients with DM may suffer from hearing impairment as a chronic complication. The effect of hearing loss may impair the quality of life of patients which affects functional, social, as well as psychological aspects. Both DM and hearing loss are considered to be associated, although this correlation remains elusive. There are three theories proposed to establish the association, which are microangiopathy, neuropathy and genetic mutation in mitochondrial DNA (mtDNA). This essay will initially discuss the importance of mtDNA mutations and neuropathy, as well as microangiopathy, in developing the expression of deafness in diabetes mellitus. It will also consider the limitation of these respective theories to explain the mechanism of hearing loss in diabetes mellitus patients.