Tachycardia does not cause fever, but fever can cause tachycardia. During a fever, the body's metabolism increases and the heart rate speeds up, a phenomenon commonly seen in colds, viral infections, and bacterial infections. After a clear diagnosis through blood tests, effective medication treatment should be administered. Once the body temperature normalizes, the tachycardia will be relieved. If the tachycardia is not caused by fever, an electrocardiogram should be conducted to determine the cause of the tachycardia, and effective medication should be used under the guidance of a doctor to adjust it.