You can tell if you have an irregular heartbeat by a sensation in your chest usually. Oftentimes patients will feel palpitations, racing, a thumping in their chest, that sort of symptomatology. A racing heartbeat may also cause symptoms of lightheadedness, dizziness, shortness of breath, so oftentimes patients will not feel it in their chest, but they'll feel generally ill. You can also take your pulse if you have a blood pressure machine at home or are skilled at finding your pulse. You will feel the heart going fast, get a sense of what's normal, and then at times you'll feel the heart really trucking away.