Cold diuresis
Also called: Cold-induced diuresis · Needing to pee when cold
Being cold makes you need to urinate. The body pulls blood away from the skin into the core, the heart reads this as too much blood, and the kidneys are told to dump water.
How common
Does this happen to you?
How it works
When you get cold, the body protects its core. The small blood vessels in the skin, hands, and feet narrow. Less blood flows near the surface, so less heat is lost1. That blood has to go somewhere. It moves into the chest and belly, where the big vessels and the heart are.
The heart and the large arteries have stretch sensors. They now see more blood than usual and higher pressure. To the body this looks like an overload of fluid. The kidneys sense the higher pressure and pass out the extra fluid, so the bladder fills quickly1. Many researchers think this pressure effect is the main cause4. An older idea is that the brain cuts back on vasopressin, also called antidiuretic hormone or ADH2. Vasopressin normally tells the kidneys to hold water2. Studies do not agree on whether cold lowers it4.
The result is a strong urge to urinate after some time in the cold. The urine is plentiful1. The amount depends partly on how much water the body holds. As the body dries out, the effect gets smaller or stops4.
Swimmers get a double dose. Cold water triggers cold diuresis, and the pressure of the water on the body squeezes extra blood into the core as well. This is called immersion diuresis1.
Is it a problem?
Not in daily life. In real hypothermia it matters. A person who has been cold for hours can lose a lot of fluid this way and become dehydrated, even though they have not been sweating3. Once they warm up, the blood vessels in the skin open again, and the total volume of blood can be too low. This is one reason rescuers give warmed fluids3.
Sources and further material
- NCBI Influence of Cold Stress on Human Fluid Balance Chapter in Nutritional Needs in Cold and in High-Altitude Environments (National Academies Press). Reviews the causes of cold-induced diuresis, including the pressure and ADH ideas.
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Related oddities
Pee shivers
A brief involuntary shudder during or just after urinating. Many people seem to get it, men more often than women. It is widely known and almost completely unstudied.
Random shivers
A single brief shudder that runs down the spine or through the whole body when you are not cold. Many people report them. Nobody has counted them.
Diving reflex
Cold water on the face makes the heart slow down, sends blood to the brain, and holds the breath. Every mammal studied so far has it. You can trigger it with a bowl of cold water.
Vasovagal syncope
The most common reason people faint. A trigger like blood, pain, heat, or standing too long makes the vagus nerve slow the heart, and blood pressure drops. The brain briefly runs short of blood and you go down.