Which of the following substances is NOT typically found in urine?

The presence of glucose in urine is not typical under normal physiological conditions. Glucose is usually reabsorbed in the kidneys, primarily in the proximal tubules, when blood glucose levels are within the normal range. However, when blood glucose levels exceed the renal threshold (approximately 180 mg/dL), the kidneys cannot reabsorb all of the glucose, leading to glucose spilling into the urine, a condition known as glucosuria.

In contrast, urea and creatinine are byproducts of protein metabolism and are normally excreted in urine. Urea is the end product of the breakdown of amino acids, while creatinine is a waste product of muscle metabolism, both of which are typically found in urine. Additionally, various drugs can be present in urine due to their metabolism and excretion, often used for monitoring drug levels or for drug screening purposes.

Thus, under normal circumstances, glucose is not present in urine, making it the correct answer to the question regarding which substance is typically absent.