The need for the delivery of insulin by injection can be reduced or eliminated by delivering aerosolized insulin. Repeatability of dosing is obtainable by using either regular insulin or monomeric insulin. When delivering insulin (not monomeric) by inhalation, the total inhaled volume should be about the same at each delivery to obtain repeatable results. The patient can be coached (by teaching) to inhale a given amount of air and can also be coached (by teaching) to inhale at a given flow rate. Further, the rate at which blood glucose is lowered is increased by the use of monomeric insulin. Particles of insulin and monomeric insulin delivered to the surface of lung tissue will be absorbed into the circulatory system. A dry powder or a liquid insulin formulation is delivered to the patient from a mechanical or electronic hand-held, self-contained device.