An immunoglobulin test measures certain immunoglobulins, or antibodies, in the blood against antigens. These antibodies are made by our body's immune system to fight against antigens, such as bacteria, viruses, and toxins. Our body produces different immunoglobulins to combat different antigens, namely IgA, IgM, IgG, IgD, IgE. The Immunoglobulin M (IgM) antibody is found mainly in the blood and lymph fluid. It is the first antibody our body creates to fight a new infection. The test is required to be taken when a person shows symptoms of an immunoglobulin deficiency. These are recurrent infections, especially of the respiratory tract (sinus, lungs) or gastrointestinal tract (stomach, intestines).