What is the normal amount of variability in IgG test results?

For adults, normal results of IgG tests range between 700 and 1,500 milligrams per deciliter or 7 to 15 grams per liter, according to WebMD. In children, normal levels vary by age, states Mayo Clinic.

An IgG test measures the amount of certain antibodies in a patient's blood, WebMD explains. However, IgG antibodies are found in all bodily fluids. Typically, at least 75 percent of all human antibodies are IgG. They primarily handle bacterial and viral infections.

IgG is the smallest type of antibody the body produces. It is the only kind that is able to cross the placental barrier between mother and fetus, notes WebMD.