High blood glucose from diabetes causes two problems that can hurt your feet:
Nerve damage. One problem is damage to nerves in your legs and feet. With damaged nerves, you might not feel pain, heat, or cold in your legs and feet. A sore or cut on your foot may get worse because you do not know it is there. This lack of feeling is caused by nerve damage, also called diabetic neuropathy (noo-ROP-uh-thee). Nerve damage can lead to a sore or an infection.
Poor blood flow. The second problem happens when not enough blood flows to your legs and feet. Poor blood flow makes it hard for a sore or infection to heal. This problem is called peripheral (puh-RIF-ur-uhl) vascular disease, also called PVD. Smoking when you have diabetes makes blood flow problems much worse.
These two problems can work together to cause a foot problem.
For example, you get a blister from shoes that do not fit. You do not feel the pain from the blister because you have nerve damage in your foot. Next, the blister gets infected. If blood glucose is high, the extra glucose feeds the germs. Germs grow and the infection gets worse. Poor blood flow to your legs and feet can slow down healing. Once in a while a bad infection never heals. The infection might cause gangrene (GANG-green). If a person has gangrene, the skin and tissue around the sore die. The area becomes black and smelly.
To keep gangrene from spreading, a doctor may have to do surgery to cut off a toe, foot, or part of a leg. Cutting off a body part is called an amputation (AM-pyoo-TAY-shuhn).