Serum free light chain combined with immunofixation electrophoresis is a test used to improve the early diagnosis of M-proteinemia. Serum free light chain is one of the tests used to diagnose M-proteinemia. It utilizes antibodies to recognize monoclonal free light chains at low concentrations and is more sensitive than immunofixation electrophoresis. It is suitable for the diagnosis of M-proteinemia, monitoring of condition and efficacy, etc., but the results may be affected by renal function. Immunofixation electrophoresis is also one of the tests for the diagnosis of M-proteinemia. Using antibodies that directly recognize heavy and light chains, it distinguishes whether the increased immunoglobulins are monoclonal or polyclonal and determines the specific type. It also confirms the presence of M proteins and is indicated to test the effectiveness of treatment for M proteinemia. Other tests used to diagnose M-proteinemia include serum protein electrophoresis, which identifies and quantifies M-proteins in the blood. These three methods are the most commonly used tests to diagnose M proteinemia and are often used in combination to improve the early diagnosis of M proteinemia and thus help in the treatment of the disease.