###Human: For the past four weeks, I have heart palpitations, shortness of breath, and fatigue. What to do? ###Assistant: Hi. Fever causes a faster heart rate. Another reason, which is not uncommon in young people, is vagal atrial fibrillation. This is an irregular fast heartbeat that occurs in bouts after eating and during resting and spontaneously revert back. What did your ECG show? Was it only sinus tachycardia or rhythm problem such as atrial fibrillation? Fever usually causes sinus tachycardia, which is a normal response to fever. When fever subsides, the heart rate slows down. Sometimes it occurs due to gastrointestinal problems, in which eating leads to insulin gush, which lowers blood sugar and sensation like blackout, weakness, palpitations, and fatigue develop. Chances of this are very low. Please send me the ECG strip so that I may diagnose your rhythm. Blood tests that might be helpful include CBC (complete blood count), U&E (urea and electrolytes), TSH (thyroid-stimulating hormone) and the ECG. These are also some rare disorders that cause a sudden rise in heart rate, fever, shortness of breath, and very high blood pressure. This condition is called pheochromocytoma, but it is extremely rare. Please tell me the other symptoms you develop along with fast heart rate feelings and fever. This along with the above tests will guide to reach a diagnosis. If the above tests are normal, I will advise you to have Holter monitoring done for 24-48 hours to catch fast heart rhythm, if not caught on ECG. Regards.