urinevolume

Urine volume is the amount of urine produced and excreted by the kidneys over a defined period, most commonly measured in milliliters per day. In healthy adults, total daily urine volume typically ranges from about 800 to 2000 milliliters, with most people producing around 1 to 2 liters per day depending on fluid intake, ambient temperature, and physical activity. Children show lower volumes that increase with age and body size.

Renal water excretion is tightly regulated by antidiuretic hormone (vasopressin) and the kidney's ability to concentrate urine. When hydration is low or plasma osmolality rises, ADH is released, increasing water reabsorption in the collecting ducts and reducing urine volume. Conversely, excess fluid intake, low plasma osmolality, caffeine or alcohol can inhibit ADH, increasing urine volume. Diuretics and certain diseases can also alter urine volume.

Measurement and normal ranges: Urine volume is usually measured over 24 hours with a collection container, then reported as milliliters per day. Normal daily volume varies with intake but generally remains within the 800–2000 mL/day range in adults. Urine concentration is described by osmolarity and specific gravity, which reflect the kidney's ability to concentrate urine at a given volume.

Clinical notes: Abnormal urine volumes may signal health issues. Polyuria is excessive urine output, commonly defined as roughly more than 2.5 to 3 liters per day; causes include diabetes mellitus, diabetes insipidus, high fluid intake, or diuretic use. Oliguria denotes reduced output (<400 mL/day) and may indicate dehydration, kidney dysfunction, or urinary tract obstruction. Anuria (<100 mL/day) is a medical emergency.