Glucose, the body's fuel, is produced by digestion and launched into the blood. At this point, the body tissues can only reach this glucose to feed on it if there is insulin present. In diabetics, insulin may be inadequate or not properly used, and the glucose continues to build up in the blood (see hyperglycemia) until the renal threshold for glucose is reached. At this point, the kidneys start to filter excess glucose from the blood and excrete it in the urine, a condition known as glycosuria. See also Renal threshold, urination, urine testing stix.