There's actually a pretty long post in the archives about this that had years of responses. It seems to be pretty young people who complain about this. It's also not necessarily true your heart is speeding up, it might just feel like it is. If it's happening a lot and it's been happening a long time, you might want to go ahead and tell your Mom about it. I admit, I never did quite understand it in that long discussion that took place, I guess you have to experience it to understand it. I'm wondering, though, since you posted in an anxiety forum, do you feel you're an anxious person? Do you have a lot of irrational fears, does nervousness get in your way a lot? Anxiety can have a ton of physiological symptoms that go alone with it if it's severe enough of a problem and lasts long enough. But it isn't responsible for everything. It could just be something you're going through at an age when things go pretty quickly through stages -- think how different you are now than when you were 13. Things move fast at your age, more slowly when you get older. It wouldn't hurt to see a doctor, again, if this happens a lot. Is there a particular time when this happens, say, right after eating? After not eating for awhile? That kind of thing.