Why do we need the bathroom more on cold days?

When a cold wind hits you, the blood vessels in your fingertips and skin narrow. This keeps warm blood from losing its heat to the outside air. It is also why your hands turn pale and cold on a chilly day.

But when less blood flows to the skin, more of it stays in the core of the body. The same amount of blood crowds into a smaller space, so the pressure inside the vessels rises a little. In effect, the body protects the warmth of important places like the heart and brain before the hands and feet.

When the body senses that there is more blood in the vessels, it tries to restore the balance. Less of the hormone that normally helps the kidneys take water back is released, so the kidneys hold on to less water and make more, weaker urine. That is why urine tends to look paler on cold days. This increase in urine caused by cold is called cold-induced diuresis.

Sweat plays a part too. Water that would leave as sweat on a hot day mostly stays in the body on a cold day, so that share also goes out as urine.

It is easy to assume it is just because you drank a lot of hot tea. How much you drink matters, but even if you drink your usual amount, getting cold makes you produce more urine. That is why you feel a sudden urge after standing in a cold wind for a long time and coming back inside.

Cutting back on water to avoid bathroom trips is not a good idea either. Water keeps leaving as urine, but you feel less thirsty than in summer, so your body can run short of water in winter without you noticing.

On days when you have to stay outside for a long time, try keeping your hands, feet and neck wrapped up warm. The skin vessels narrow less, which may mean fewer bathroom trips. Before a winter hike or an outdoor event, it also helps to find out where the restrooms are. Once you get somewhere warm and your body relaxes, the extra urine gradually returns to normal.

It is better to drink water a little at a time than a lot at once. If you go far more often than usual or it hurts, whatever the weather, have it checked at a clinic.