What is the difference between a symptom and a sign?

Medical Author: William C. Shiel Jr., MD, FACP, FACR

A symptom is any subjective evidence of disease, while a sign is any objective evidence of disease. Therefore, a symptom is a phenomenon that is experienced by the individual affected by the disease, while a sign is a phenomenon that can be detected by someone other than the individual affected by the disease. For examples, anxiety, pain, and fatigue are all symptoms. In contrast, a bloody nose is a sign of injured blood vessels in the nose that can be detected by a doctor, a nurse, or another observer.

Health-care professionals use symptoms and signs as clues that can help determine the most likely diagnosis when illness is present. Symptoms and signs are also used to compose a listing of the possible diagnoses. This listing is referred to as the differential diagnosis. The differential diagnosis is the basis from which initial tests are ordered to narrow the possible diagnostic options and choose initial treatments.

Our Symptom Checker for children, men, and women, can be used to handily review a number of possible causes of symptoms that you, friends, or family members may be experiencing. There are many causes for any particular symptom, and the causes revealed in the symptom checker are not exhaustive. That is, they are not intended to be a listing of all possible causes for each symptom but are representative of some of the causes that can be underlying various symptoms.