As a health and physiology expert, I'd like to delve into the factors that influence the time it takes for the body to process and excrete water after consumption. The process of urination, or micturition, is a complex physiological function that involves several systems within the body, including the urinary, circulatory, and nervous systems.

Firstly, the Glomerular Filtration Rate (GFR) is a key indicator of how efficiently the kidneys filter waste and excess water from the blood. As you mentioned, GFR does decline with age, which can affect the rate at which the body processes fluids. However, a healthy individual typically maintains a GFR within a normal range, which allows for the effective filtration of the blood.

The amount of urine produced in a 24-hour period, as you've noted, can vary significantly from person to person, ranging from 800 to 2000 ml. This variation can be influenced by several factors, including fluid intake, the body's hydration state, physical activity levels, and environmental conditions such as temperature and humidity.

When a person drinks a glass of water, the journey from ingestion to excretion begins in the gastrointestinal tract. The water is absorbed into the bloodstream through the walls of the stomach and intestines. From there, it is transported to the kidneys, where it is filtered and excess water, along with waste products, is formed into urine.

The bladder, which is a muscular sac, serves as a temporary storage for urine. A healthy bladder can comfortably hold up to 16 ounces, or approximately 2 cups, of urine. The sensation to urinate typically arises when the bladder is about half full. However, the actual time it takes for the bladder to reach this point can vary greatly. It can be as short as 2 hours or as long as 5 hours, depending on the individual's physiological state and the factors mentioned earlier.

The nervous system plays a crucial role in the timing of urination. The micturition reflex is triggered when the bladder wall stretches due to the accumulation of urine. This reflex sends signals to the brain, which then decides whether it is appropriate to initiate the process of urination based on the individual's circumstances.

It's important to note that the rate of urination can be influenced by the presence of certain medical conditions, such as urinary tract infections, diabetes, or prostate issues, which can either increase or decrease the frequency of urination.

In conclusion, while there is a general range for how long it might take to urinate after drinking a glass of water, the actual time can be highly variable and depends on a multitude of factors. Understanding one's own body and its signals is key to maintaining proper hydration and urinary health.

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GFR does decline with age. A healthy person drinking approximately 2 liters of water per day makes 800 to 2000 ml of urine per 24 hours (4). If the urinary system is healthy, the bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours (5).read more >>