OverviewA thermometer is a useful aid used to measure body temperature. A thermometer is usually filled with mercury. Mercury in the tube rises when expanded by an increase in body temperature.
Update Date 12/7/2014
Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.