Hi.. There are multiple causes for fast heart rate, known as tachcardia. A few of the causes include psychological such as the anxiety, stress and others.. Other are pathological which needs to be treated.. Conditions such as anaemia, infections, thyroid dysfunctions and other hormone dysfunctions, cardiac problems and so on... And Of all these parameters the psychogenic causes are the most common.. Modifications in the management of stress and anxiety, reducing caffeine intake, cutting down on smoking will help in reducing the symptoms.. If the symptoms persist consult your doctor who can advice you on the tests to be done and the use of beta blockers and other medications..