Battery issue with my iPhone 5?

I've been using an iphone 5 since september and recently the battery decides to crap out (the phone switches off) when the battery is at 25% or less (e.g. 10%) and the phone won't turn back on (displays a low battery symbol) for a while, it will eventually turn back on without charging it up, just wondering if this is covered by Apple's standard 1 year warranty and whether I could get the phone replaced? I'd usually expect the phone to power down under 5% but for it to crap out at 10-25% is really annoying.

Maybe it's battery just like that

I think you need to go to apple they can fix it or give you a new one for free I dropped my iPad and then they gave me a new one cuz I broke it