You can’t judge whether a patient’s condition is serious only from how much low complement C1q is, but you have to make a comprehensive analysis from the causes of low complement C1q, the specific condition and the patient’s personal constitution, etc. Low complement C1q is mostly seen in immune system-related diseases such as mixed connective tissue disease, systemic lupus erythematosus, and other immune system-related diseases. Complement C1q is a glycoprotein with the function of adjusting immune cells and maintaining immune tolerance, produced by mast cells, immature dendritic cells and macrophages, and its elevation or decrease has certain clinical significance, in which the decrease of complement C1q is commonly seen in mixed connective tissue disease, systemic lupus erythematosus, nephrotic syndrome and other immune system-related diseases. Complement C1q lower than the lower limit of the reference range is abnormal, but only from the low complement C1q can not judge whether the patient’s condition is serious or not, need to be based on the patient’s age, whether accompanied by the underlying diseases and whether the diagnosis of mixed connective tissue disease, systemic lupus erythematosus and other diseases to analyze the above factors are different, the patient’s condition will be there are greater differences, can not be generalized. Laboratory test results should be interpreted by a professional physician, and it is recommended that patients go to the rheumatology and immunology department of a regular hospital in a timely manner for treatment under the guidance of a doctor.