How to solve my Battery life issue on IPhone?

Okay so like today I charged it in the morning it wS completely dead so I charged it and it took not even an entire hour to charge it took about 35 minutes to fully charge and an hour and a half later it was dead. My battery life really sucks does any body know how to re solve this?

Plug it in

It sounds like your battery needs replacing. A rechargeable battery gets less efficient over time and eventually it will get to the stage where the phone will not work unless its plugged into the mains. Contact Apple and they'll replace the battery. If you have had the phone under 2 years, the battery will be replaced free of charge; over 2 years and you'll be invoiced for it. If you have acquired the phone very within the last month and it was brand new then you need to return it to the place you brought it from; as the battery could have been defective from new.