Temporary episodes of hyperglycemia or high blood sugar often do not cause symptoms. The blood sugar level may rise well above normal for significant periods without causing any side effects.
However, chronic hyperglycemia where the blood sugar is persistently higher than normal can lead to a wide variety of serious complications including nerve damage, eye problems, kidney damage, cardiovascular damage and problems with the feet and legs.
Listed below are some of the effects of both acute and chronic hypergylcemia. The first three described form the class hyperglycemic triad.