The present invention is directed to treatment methods for a disease or condition, in a subject in need of such treatment, that provide alternatives to treatment by injection that give, relative to treatment by injection, improved treatment outcomes, 100% treatment compliance, reduced side effects, and rapid establishment and/or termination of substantial steady-state drug delivery. The method typically includes providing continuous delivery of a drug from an implanted osmotic delivery device, wherein substantial steady-state delivery of the drug at therapeutic concentrations is typically achieved within about 7 days or less after implantation of the osmotic delivery device in the subject and the substantial steady-state delivery of the drug from the osmotic delivery device is continuous over a period of at least about 3 months. In one embodiment, the present invention is directed to treatment of type 2 diabetes mellitus using incretin mimetics.