Complement C1q below the normal reference range suggests that the patient may have an autoimmune disease. Complement C1q belongs to complement C1, which is often involved in inflammation and immune response, therefore, when the result of complement C1q test is lower than the normal reference range, it suggests that the patient may have autoimmune diseases, such as systemic lupus erythematosus, dermatomyositis, desiccation syndrome, autoimmune hemolytic anemia and so on. Patients with low complement C1q should further improve autoantibodies, blood sedimentation, ultrasound and other related auxiliary tests to clarify the causes of the abnormal results of the test and timely treatment for the causes. Laboratory results should be interpreted by a professional physician, and it is recommended that patients with low complement C1q go to the rheumatology and immunology departments of regular hospitals for detailed consultation.