Diabetes mellitus causes a decrease in the function of macrophages due to elevated blood glucose, resulting in an increase in the number of infections: 1) tuberculosis infections; 2) Staphylococcus aureus infections, especially when there are skin infections and breaks in the epidermis, and after the infection occurs, Staphylococcus aureus can colonize the tissues of the body through the broken tissues and through the blood circulation, i.e. bloodstream infections; 3) Klebsiella pneumoniae infections, mainly due to high blood glucose. It causes the macrophages in the liver, that is, the function of liver blast cells to decrease, and the bacteria that migrate into the blood from the intestine and urinary tract cannot be completely removed in the liver, and then enter the blood and lungs. 4, fungal infections, Trichoderma and Aspergillus infections will increase. In addition, diabetes can also cause an increase in inhalation infections, because the immunity of the airway is also affected, and also prone to inhalation bacterial infections.