The behavior of mineral levels in the diet and serum of diabetic patients was investigated. The gustometry was also examined to identify the relationship between zinc deficiency and hypogeusia. The serum levels of zinc and iron in diabetic patients were lower than those in healthy people, and the sensitivity of taste, especially of sweetness, in diabetics was also lower than that in healthy people. These findings suggest that the lower sensitivity for sweetness in the diabetic patients induced them to eat more sweet foods. A survey of the zinc, iron and copper levels in the diets of the diabetic patients indicated lower values than the dietary recommendations. In particular, the dietary zinc and iron levels of the diabetic patients who were consuming a restricted-energy diet were significantly lower than the recommended values, suggesting the importance of good mineral balance in the diet for diabetics. These results suggest the importance of studying the relationship between the diabetic serum mineral level and the mineral level of the meal.