Urine volume (24h)
What it measures, and what changes the number.
This is the total volume of urine collected over a full day. On its own it reflects fluid intake and kidney water handling, but its main role on a lab report is to support other timed urine tests.
It is recorded whenever a day-long collection is done, so it appears next to tests such as total daily protein, urine protein concentration, creatinine clearance and urinary free cortisol. Those results are calculated from concentration multiplied by volume, so an accurate volume is essential.
The figure depends entirely on the collection being complete: the first morning void is discarded, then every void is saved until the same time next morning. Missed or spilled samples lower the volume and every result derived from it. Drinking habits on the collection day also change it. Spanish labs may print it as Diuresis.
Often read alongside: Urine protein excretion (24h), Urine protein (24h), Creatinine clearance, Urinary free cortisol (24h)