injectable insulin formulations with improved stability and rapid onset of action are described herein . the formulations may be for subcutaneous , intradermal or intramuscular administration . in the preferred embodiment , the formulations are administered via subcutaneous injection . the formulations contain insulin in combination with a chelator and dissolution agent , and optionally additional excipients . in the preferred embodiment , the formulation contains human insulin , a zinc chelator such as edta and a dissolution agent such as citric acid . these formulations are rapidly absorbed into the blood stream when administered by subcutaneous injection . in the preferred embodiment , the insulin is provided as a dry powder in a sterile vial . this is mixed with a diluent containing a pharmaceutically acceptable carrier , such as water , a zinc chelator such as edta and a dissolution agent such as citric acid shortly before or at the time of administration . in another embodiment , the insulin is stored as a frozen mixture , ready for use upon thawing .