The kidneys hold on to water
Vasopressin reaches the kidney, where the collecting duct becomes more permeable to water, so more water returns to the blood and less leaves as urine.
A day of low fluid intake — 0 seconds
Follow how the body defends its water over a day when fluid intake stays low.
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Time elapsed
- Low intake begins · 00:00:00
- A small deficit builds · 04:00:00
- Water conservation ramps up · 08:00:00
- Thirst and blood concentration rise · 13:00:00
- Urine is highly concentrated · 18:00:00
- One day on · 24:00:00
Happening now
Fluid intake is low while the usual routes of water loss carry on.
Explore the mechanism Water keeps leaving
Water leaves the body through the kidneys, the skin, the breath and the gut, even when little is coming in.
Evidence for this step
Water typically leaves the body without pause through the kidneys, skin, breathing and the gut, so a day with little fluid intake usually produces a net body-water deficit. moderate · View sources
- Whole-body context: 10%
- Kidneys: 30%
- Nephron and collecting duct: 25%
- Bloodstream: 20%
- Endocrine signalling: 15%