We claim a method of lowering plasma glucagon in a subject in need thereof comprising administering to the subject a composition comprising a modified exendin or modified exendin analog, wherein said modification comprises one or more molecule linked to an exendin or the exendin analog wherein said molecule is selected from the group consisiting of polyethylene glycol, gelatin and/or albumin. The modified exendin or the modified exendin analog has activity of suppressing glucagon secretion and/or lowering glucagon levels in the subject and possesses increased biological half-life compared to unmodified exendin or unmodified exendin analog. The method is useful in treating hyperglucagonemia and other disorders that would be benefited by lowering plasma glucagon or suppressing glucagon secretion.