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 patient's blood.
Blood titer measurements can be very helpful in determining medical treatment. Antibody titers can tell the doctor if the patient has immunity to diseases such as measles , chickenpox, and hepatitis . They can also help measure harmful antibodies related to lupus.
A titer measurement is expressed as a ratio, such as 1:40.