It has been discovered that by combining a chelator, such as ethylenediaminetetraacetic acid, with an acidifier, such as citric acid, the insulin is absorbed much more rapidly than in the absence of the chelator and acidifier, with a commercially available rapid, intermediate or long lasting insulin such as glargine, one can increase and/or prolong the bioavailability of the insulin mixture. The formulations are suitable for administration by injection or to a mucosal surface such as the pulmonary or oral regions, although subcutaneous injection is preferred.