According to MedlinePlus, the ESR, or "sed rate," should be less than 15 millimeters per hour for men under 50 years old, while for men over 50, a normal reading is less than 20 mm/hr. That is the same sed rate for women under 50, although it should be less than 30 mm/hr for women over 50, MedlinePlus reports.
MedlinePlus indicates that, for newborns, a normal sed rate is 0 to 2 mm/hr, while, between infancy and puberty, a normal reading for a child is 3 to 13 mm/hr.
According to KidsHealth, an ESR --erythrocyte sedimentation rate-- blood test is used to determine the level of infection inside a person's system. KidsHealth explains that the test measures the sinking of red blood cells because, if an infection is present, red blood cells tend to stick together and fall at a faster rate.
MedlinePlus states that an ESR test is performed on patients with unexplained fevers, some forms of arthritis and unexplained and non-specific symptoms. While the test does indicate the presence of an infection, it does not diagnose a specific illness, MedlinePlus relates. However, it often provides evidence to help identify conditions such as autoimmune disorders, tissue death and tuberculosis. Once an illness is diagnosed, MedlinePlus observes that ESR tests are used to monitor patients.