Lack of energy
Diabetes is fundamentally an alteration in the metabolism of carbohydrates, which is the same as the production of energy. People with diabetes usually have a resistance to the action of insulin, a hormone that opens the gate for glucose to enter the cells to give them energy. Thus, patients with diabetes feel low energy levels as a result of a low level of energy being produced in their cells. Instead of staying inside to give us energy, glucose does not leave the blood and reaches a high and sometimes dangerous level.
This would also explain why people experience unusual hunger. Their organism is led to believe that they need more nutrients because there are not enough carbohydrates inside the cells. The brain interprets this signal and triggers hunger as a reflex mechanism to get more energy from foods.