A titer is a measurement of the amount or concentration of a substance in a solution. It usually refers to the amount of antibodies found in a person's blood.
Blood titer measurements can help determine medical treatment. Antibody titers show if a person is immune to diseases such as measles, chickenpox, or hepatitis. They can also help measure harmful antibodies related to lupus.
A titer measurement is expressed as a ratio, such as 1:40.
Ashihara Y, Kasahara Y, Nakamura RM. Immunoassays and immunochemistry. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 44.
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.