The most obvious reason that you have cold feet is because your feet are cold. If it’s cold enough to wear a jacket and your feet are bare – maybe you just need to put on some socks. However, there could be medical reasons that your feet are cold.
It’s possible that not enough (warm) blood is getting to your feet. This could be due to poor circulation when the heart can’t pump well enough or from not moving around enough. With exercise, the leg muscles help the veins return blood to the heart allowing fresh blood to enter the feet. It’s counter-intuitive, but blood flow is better with leg elevation so too much sitting can be a problem. Smoking causes blood vessels to constrict, also reducing reducing blood flow. Raynaud’s phenomenon, which causes blood vessel spasm from cold, can be so severe as to temporarily cut off blood supply entirely.
An underactive thyroid can reduce the body’s temperature and heart rate. Both of these can cause cold feet. A partially clogged artery due to high cholesterol will reduce the blood flow to the lower extremities. Not only will there be cold feet, but also pain with exercise since the muscles will not have enough oxygen-rich blood.
Nerve damage can give the sensation that the feet are cold as well as reduce blood flow. An unfortunately common cause of this kind of damage is diabetes.
What to do? First, put on a pair of socks and get some exercise. The next step is to check with your physician to make sure that you don’t have any underlying disease that causes cold feet.