From the Guidelines
The normal range of urine production in adults is typically 0.5-1 ml/kg/h, as indicated by the most recent and highest quality study 1. This means that a 70 kg adult would normally produce about 35-70 ml of urine per hour.
- Urine output can vary based on several physiological factors including:
- Hydration status
- Fluid intake
- Environmental temperature
- Medication use
- Urine output below 0.5 ml/kg/h for several consecutive hours may indicate acute kidney injury or other renal problems, while sustained output above 1 ml/kg/h might suggest diabetes insipidus, excessive fluid intake, or the effect of diuretic medications.
- In clinical settings, urine output is an important vital sign that helps assess kidney function and overall fluid balance.
- The kidneys regulate urine production through complex mechanisms involving filtration at the glomerulus and reabsorption in the tubules, responding to signals from hormones like antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system to maintain appropriate fluid balance in the body. The definition of acute kidney injury (AKI) includes a urine output of less than 0.5 ml/kg/h for 6 hours, as stated in the study 1. However, the most recent study 1 provides a more comprehensive understanding of urine production and its relation to kidney function, making it the most reliable source for determining the normal range of urine production.
From the Research
Normal Range of Urine Production
The normal range of urine production in milliliters per kilogram per hour (ml/kg/h) can vary depending on several factors, including the individual's health status, fluid intake, and kidney function.
- A study published in 2017 2 found that a minimum hourly urine output target of 0.2 mL/kg/h was noninferior to the standard target of 0.5 mL/kg/h in patients undergoing major abdominal surgery.
- Another study published in 1987 3 examined the factors affecting urine volume in patients with chronic renal failure and found that total osmolar excretion correlated highly with urine output.
- A 2003 study 4 found that high urine volume and low urine osmolality were risk factors for faster progression of renal disease, suggesting that high fluid intake may not slow renal disease progression in humans.
Urine Output Targets
The optimal urine output target can vary depending on the individual's specific needs and health status.
- The 2017 study 2 suggests that a target of 0.2 mL/kg/h may be suitable for patients undergoing major abdominal surgery.
- The 1987 study 3 highlights the importance of considering total osmolar excretion when evaluating urine output in patients with chronic renal failure.
- The 2003 study 4 suggests that patients with chronic renal insufficiency should generally let their thirst guide fluid intake, rather than pushing fluids to achieve a specific urine output target.
Clinical Significance
Urine output is an important indicator of kidney function and overall health.
- A 1988 study 5 discusses the clinical significance of relative density of urine and its relationship to kidney function and disease.
- The 2003 study 4 found that sustained high urine volume and low urine osmolality were independent risk factors for faster glomerular filtration rate decline in patients with chronic renal insufficiency.