And what is happening with organism on such cases..

As insulin producing a pancreas gland, as he needing for glucose absorbing by organism, as in insulin taking part a sugar lowering in blood, and healthy person eating till one kg of candies and non bad effects getting,but in insulin resistance  a glucose stops transfers in tissues and filling in blood, and pancreas wondering will hit in blood a high portion of insulin, as this process for long time forming as non symptomatic, as a good a high sugar found in research, but disease found on latest stages,when sugar in norm as 3.5-5.5 is having 12, or in complications are infarcts, blindness, strokes, head brain damage, kidneys, gangrene..
In a high glucose level you are feeling a high thirst, dryness mouth, urination, as on sweet process forming Candida's, and other fungus, where are not allowing healing on skin are wounds, scratches..