Normal Urine Output During Urination
In healthy adults, a typical single void produces approximately 200-300 mL of urine, though normal volumes can range from 150-600 mL depending on bladder capacity and fluid intake. 1
Volume Parameters by Clinical Context
Healthy Adults
- Normal voided volumes range from 150-600 mL per void, with no artificial minimum restriction necessary for assessing normal voiding function 1
- Peak urinary flow rates correlate directly with voided volume, with volumes above 100 mL considered the minimum acceptable for reliable flow rate assessment 2
- Individual voiding volumes show considerable variation even in the same person, ranging from less than 50 mL to more than 200 mL at different times 3
Frequency and Volume Relationship
- Asymptomatic women void a median of 7-8 times per 24 hours, with 95% voiding fewer than 13 times daily 4
- Mean voided volume and maximum voided volume remain stable over time in individuals without lower urinary tract symptoms 4
- The number of voids per liter of fluid intake represents the most stable measure of voiding patterns 4
Clinical Thresholds for Abnormal Output
Oliguria Definitions
- Oliguria is defined as <0.5 mL/kg/hour sustained over at least 6 hours, which translates to approximately <400 mL per day in a 70 kg adult 5
- Anuria is defined as 24-hour urine volume less than 100 mL 6
- These thresholds apply to total daily output, not individual void volumes 5
Nocturia Considerations
- Normal nighttime voiding produces normal or large volume voids when nocturnal polyuria is present (>33% of 24-hour output occurring at night) 7, 8
- Small volume voids throughout day and night suggest reduced bladder capacity rather than polyuria 8
Important Clinical Caveats
Do not confuse single void volume with hourly urine output rates - these measure different physiologic parameters. Single void volume reflects bladder capacity and voiding habits, while hourly output rates (mL/kg/hour) assess kidney function and perfusion 5
The wide normal range (150-600 mL per void) means that individual variation is substantial, and serial measurements in the same patient are more informative than single values 1, 4