The second stage of urine formation, tubular re-absorption, is called selective re-absorption The filtrate enters the kidney in the proximal tubule. This region of the kidney is special because many things can be removed from the filtrate. These valuable things are recollected, or reabsorbed, by the body.
Glucose, certain salts, vitamins, hormones, and amino acids are restored to the body and will not be included in urine. Sometimes, if the body has too much of something then the extra sugar or salt will stay in the filtrate. For example, diabetics with high levels of blood glucose may have glucose in their urine since it cannot all be reabsorbed. The filtrate after reabsorption is like pre-urine.