The aim of the present study was to identify clinical and audiologic characteristics of idiopathic sudden hearing loss (ISHL) in patients with type 2 diabetes. We retrospectively investigated 148 cases of ISHL, whose age was more than 40 years, comparing clinical and audiologic valuables between diabetic and non-diabetic patients. Twenty-four patients (16.2%) had type 2 diabetes (16 male, 8 female). Prevalence of hypertension and hyperlipidemia were significantly greater in diabetic patients. Hearing in the affected ear was more impaired in diabetic than non-diabetic patients, although hearing in the unaffected ear and degree of recovery did not differ significantly. Mean BMI, duration of diabetes, HbA1c values, and ultrasonographically determined carotid intima-media thickness (IMT) and plaque scores in diabetic patients with ISHL were 24.0+/-3.7 kg/m(2), 9.8+/-7.8 years, 7.8+/-1.5%, 0.83+/-0.16 mm, and 3.8+/-2.8, respectively. Of 17 diabetic patients whose ISHL was treated with steroids, 12 required insulin for glycemic control during treatment. Compared with diabetic patients without ISHL, HbA1c value was significantly higher in diabetic patients with ISHL (7.2+/-1.2% versus 7.8+/-1.5%, P=0.0202). In conclusion, nearly 16% of our patients with ISHL had type 2 diabetes, and this subgroup was associated with more severe hearing loss. Further studies are needed to determine which subgroups of diabetic patients are most likely to develop ISHL, which patients are predisposed to more severe hearing loss, and how various factors and treatments influence outcome.