Why Cold Weather Makes You Urinate More Often

Have you ever noticed that you need to pee more often in winter, or when you are in a really cold room? This happens because of a perfectly normal phenomenon known as cold diuresis.

Cold diuresis
In cold weather, your body tries to keep your core warm by constricting your blood vessels and reducing the flow of blood to your skin. This process is called vasoconstriction. It is necessary because heat is lost from your skin to the environment, so your body tries to reduce the flow of blood to your extremities, especially your fingers and toes.

The constricted blood vessels cause your blood pressure to rise, because the same amount of blood has less space to flow through. To regulate your blood pressure, your kidney filters out some of the excess fluid from your blood, to reduce its volume. As your bladder fills up with the excess fluid, you feel the urge to pee. A full bladder is another way that your body loses heat, so urinating immediately helps preserve your core warmth.

The reverse happens in summer
This entire process gets reversed in summer, and is known as vasodilation. Your body tries to cool itself by dissipating heat through your skin, in a process we are all too familiar with: sweating. As the external temperature rises, your blood vessels dilate, so that your blood flow is increased. As your blood comes in contact with the surface of your skin, the excess water from your blood evaporates, cooling your skin.

What factors affect this process?
There is no fixed temperature at which your body begins to cool or warm itself. At every given point of time, the human body is trying to maintain homeostasis, which is a state where factors like temperature, pH, nutrition, etc. are stable. So if you are feeling warm, your body will try to cool itself and if you are feeling cold, your body will try to maintain its warmth. The factors that affect this process are age, gender, body composition, diet and exercise, and these factors differ from person to person. A study has shown that one way to prevent cold diuresis is to exercise in cold weather.