A 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.
Review Date 8/7/2019
Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.