Pee shivers

How it works

Emptying the bladder is run by the autonomic nervous system, the part of the nervous system that works without conscious thought. It has two sides². The parasympathetic side relaxes and empties. The sympathetic side holds, tightens, and also controls blood pressure and shivering². Urinating needs a switch from sympathetic to parasympathetic control and then back again.

The leading idea is that signals cross during that switch. A burst of sympathetic activity, meant to restore blood pressure as the bladder empties, sets off the shiver reflex by mistake¹. A second idea is that the drop in blood pressure itself triggers the shudder. A third is that losing a volume of warm urine drops the body’s core temperature a little¹. None of these have been tested.

Internet surveys report the shiver in about 83% of males and about 58% of females¹. No peer-reviewed study of how common it is exists¹. Standing to urinate may make it more common, which would explain part of the difference between men and women, but this has not been tested either.

How common it is

Very common, on the evidence of surveys and forums. The medical name sounds official but it does not appear in any medical classification¹. It was adopted online and doctors have not replaced it. This is one of the most widely shared body experiences with the least research behind it.