I had the battery on my macbook go out within a year of owning the computer. It suddenly dropped from like about 80% battery health to a matter of 35% to 15% over the period of a few days. They sent me a replacement one out of warranty (But for free, long story...) and that one lasted about another 8 months before it stopped charging and I had to get another one. I'm on my third one right now, and I'm at about 75% health with it on 211 cycles. I'm surprised that having owned your computer for longer than I have, you have significantly less cycles on your battery.
Chances are if you call in, you're going to have to have to do stuff like try resetting the PRAM and what not first before they will do anything about it. (I forget what exactly this does, but it helped my battery last about a month longer or something before it was low enough that they would replace it under its first warranty) I forget how to do it too, but you could probably google it. What program are you using to determine your battery specifications? Try downloading iStat Pro and see what it says about the health of your battery?