iphone 4 battery suddenly draining fast when not in use

[jessie2sexy]

I have an Iphone 4 on iOS 6.1.3 that I havent really had any problems with, with the exception of the last 2 days. The battery has suddenly started draining incredibly fast despite me not touching it, for example while I was at work my phone was at 100%(8 AM) but by lunch time(12 PM) it was at 50% and I wasn't even able to touch it. When I got off work at 3 PM it was at 35%. I havent changed anything about it recently and was just wondering what could have caused this? I read on another forum about my mail/calendars being the cause of the problem so I have deleted them but it still hasn't seemed to fix it. If anyone knows what could be causing this, I would appreciate any help you can give me.

 

[hoben02]

Are you using your wifi at work if not turn it off so it doesn't keep trying to connect.