A layer of foam after the urine foam dissipates may be caused by high blood sugar, proteinuria, urinary tract infection and other reasons. 1. Higher blood sugar: patients with high blood sugar, the concentration of glucose in the urine may increase, which leads to an increase in the surface tension of the urine, so there is a layer of floating foam after the urine foam dissipates. 2. proteinuria: patients who suffer from proteinuria, the density of urine in the body may increase at any time, so the surface tension may increase, and ultimately there is a layer of foam after the dissipation of urine foam. 3. Urinary tract infection: If the patient is suffering from urinary tract infection, the red blood cells and white blood cells in the urine may increase, which may lead to an increase in the number of bubbles when urinating. There may be other reasons for this condition, it is recommended to go to the hospital for the appropriate examination to find the cause and then targeted treatment.