Protein electrophoresis and immunofixation are subject to a variety of analytical interferences that may affect monoclonal protein diagnostics performed in the context of monoclonal gammopathies. Interferences include endogenous substances, such as hemoglobin and fibrinogen, and exogenous compounds, such as radiocontrast dyes, antibiotics, and monoclonal antibody therapies. General approaches to managing interferences begin with recognition of the problem. Provided herein are examples of common, rare, and novel interferences with the goal of providing a comprehensive overview. With each example, specific methods and strategies are provided to manage analytical interferences to ensure that interpretative reports are accurate. Longstanding and newer technologies are also described to contextualize where interferences may be identified and avoided.