Diabetic ketoacidosis
Because the cells still do not have enough glucose to create the energy they need, the liver also breaks down glycogen to make more glucose.  (The body stores sugar in different forms in case it needs energy later.  Glucagon helps break down some of these sugar stores into glucose.)  However, there is still not enough insulin in the blood to break down the glucose into energy.  Because of this, the glucose stays in the blood (making the blood sugar levels get even higher) and the cells keep starving.