Being sick can cause an elevated heartrate, or sinus tachycardia, states Mayo Clinic. Most people with sustained high heartrates have underlying illnesses or conditions, such as anemia, infection or raised thyroid hormone levels. Some people, especially women between 20 and 40, experience sinus tachycardia when recovering from viruses.
There are other causes for continuous heartrates of 100 to 130 beats per minute, Mayo Clinic explains. For instance, some people's bodies react to certain medications with elevated heartrates. In certain cases, an excessive amount of daily caffeine has the same effect. A fast heartrate is occasionally a symptom of a serious medical problem, such as atrial fibrillation or irregular heartbeat.