Diabetes has many possible complications, including nerve damage (neuropathy). Over time, excess blood sugar can injure the walls of the tiny blood vessels (capillaries) that nourish the nerves. This can cause tingling or numbness that usually begins at the tips of the toes or fingers and over a period of months or years gradually spreads upward. Left untreated, it's possible to lose all sense of feeling in the affected limbs.
If you have any degree of nerve damage, you may not be able to sense if an electric blanket or heating pad is too hot — which can lead to inadvertent burns. The same issue applies to water temperature when bathing.
If you have diabetes and would like to use an electric blanket, warm up your bed with the blanket before bedtime — then turn the blanket off or remove it from the bed before you climb in.