IPhone keeps dying but not at 1%

Question

Sometimes my phone dies at 20% or approximately 17%. I plug in my iPhone and it goes automatically back to 20%.
I don't know whether this is relevant or not, but sometimes it may jump to 1% from like 25% and then when I plug it back in it's back to 25.
i only charge my phone once a day, and I normally let it die out (or very close to it.)
These problems have persisted for a while and have occurred with all updates I have. 
Im currently on the latest software (7.1.2) and it did it again today.
I've reset my phone several times to no avail.
i have two months warranty left on my 5S so should I take it to apple and hope they replace it?

Answer 1

Make an appointment at the genius bar. They can test the battery. My iPhone 5 was doing the same thing at around 40% or so. When they tested it, they determined the battery was failing. Only holding about 60% of a charge. Mine was replaced under the iPhone 5 battery replacement program. They should replace yours under warranty if it's bad.