Rheumatoid factor less than 20U/ml is normal. 1. Rheumatoid factor is an autoantibody used to assist in the diagnosis of rheumatoid arthritis, and can also be used to assist in the diagnosis of other autoimmune diseases, such as systemic lupus erythematosus, desiccation syndrome, and polymyositis. In addition, certain infectious diseases such as infectious mononucleosis, tuberculosis, etc. will also have elevated rheumatoid factor. 2. Rheumatoid factor is normal if it is less than 20U/ml and the patient has no uncomfortable symptoms. If the rheumatoid factor is elevated in the laboratory, you should go to the hospital for further examination to clarify the cause and treatment under the guidance of the doctor. Elevated rheumatoid factor is common in patients with rheumatoid immune system diseases or certain infections such as tuberculosis, etc. Therefore, patients with elevated rheumatoid factor should consult a doctor in time to clarify the cause of the disease and then treat it.