Low complement C3C4 can be caused by many reasons, such as immune diseases, low immune function, cirrhosis, etc. It is necessary to go to the hospital to clarify the cause of the problem and then treat the cause of the problem. 1. Complement C3C4 is an integral part of the body’s immune function, when the body’s immune function is in trouble, it can cause low complement C3C4. 2. Clinical causes of low complement C3C4 include: (1) Immunologic diseases, such as systemic lupus erythematosus, chronic glomerulonephritis, etc., can have low complement C3C4. (2) Low complement C3C4 can also occur in low immune function, such as severe infections and burns. (3) Low complement C3C4 can also occur in other cases such as cirrhosis. 3. The treatment of low complement C3C4 needs to be different according to the cause of the disease. For example, if low complement is found in systemic lupus erythematosus, glomerulonephritis, etc., active anti-inflammatory and immunosuppressive treatment is needed; if severe infection, burns, etc., active anti-infective and anti-shock treatment is needed; if cirrhosis, etc., liver-protecting treatment is needed. Therefore, if there is a low complement C3C4 in the test, it is necessary to go to the hospital in time to clarify the cause of the disease, and standardize the treatment under the guidance of the doctor.