Health anxiety (also referred to as illness anxiety disorder) involves excessive fears about having or developing a serious illness. These fears are often accompanied by a range of excessive health behaviors, including checking the body for signs or symptoms of an illness, considerable time spend engaging in internet research about health conditions, and seeking out numerous medical tests or opinions.

Other individuals with health anxiety avoid health-related information, as well as heath care professionals. Some people with health anxiety have worries that primarily focuses on a single health problem (i.e., cancer, a neurological disease), whereas others may be worried about a range of health problems over time.