Dear doctor, Recently, I have been experiencing heart palpitations, or rapid and thumping heart beats since yesterday night. I suspect that this is resulted from taking a supplement that contains caffeine. Although I have been taking in caffeine for few months now, I only take in around 200 mg of caffeine. Still, I was wandering how long the heart palpitations will last? Should I be concerned about this? I feel very little tightness in my left chest which is where the heart is located. I am only 18 years old. Thank you.