When blood sugar increases in the elderly, it may bring the following kinds of harm: First, elevated blood sugar will increase blood viscosity on the one hand, and make blood vessels thinner, more brittle and less elastic on the other hand. Second, elevated blood glucose causes the accumulation of cholesterol in nerve cells and circulatory system disorders, so that nerve cells do not receive adequate blood oxygen supply, which directly causes malnutrition and obstructive changes of nerve cells. This leads to peripheral neuritis, plant nerve disorders and other neurological diseases. Third, sugar, fat and protein are the three basic substances of human metabolism. High blood sugar leads to disorder of sugar metabolism, which breaks the balance of system metabolism, and then leads to disorder of lipid metabolism, resulting in problems of the whole metabolic system. Fourth, elevated blood sugar in the elderly will also bring other hazards, such as causing dehydration and hypertonic coma, electrolyte disorders and acidosis, leading to insulin failure and wasting.