The answer in a healthy individual is 100% of the glucose is reabsorbed from the filtrate in the nephrons of the kidneys. These tiny nephrons are the structural and functional units of the kidney. They regulate the concentration of water and soluble substances by filtering the blood. They also regulate a person's blood pressure. Excess water, the waste urea and some salt is excreted in the form of urine. Actually, two thirds of the filtered salt and water get reabsorbed into the circulating blood, along with all of the filtered organic solutes--these include glucose and amino acids. If a person has diabetes however, sometimes, excess glucose will be present in their urine and can be detected by a sugar test of the urine. The glucose should not be excreted in the urine and this is an indication of diabetes.