Carcinoembryonic antigen test has more aspects to pay attention to, such as not smoking before the blood test, not eating some sugary, greasy food, and so on. Carcinoembryonic antigen belongs to one of the tumor marker tests, which is mainly used to assist in the diagnosis of malignant tumors, detecting the efficacy of treatment, judging the prognosis, and the index of tumor recurrence, when smoking may lead to a mild increase in the value of carcinoembryonic antigen, therefore, smoking should be avoided before the test. Eating some greasy food will lead to the elevation of blood sugar and blood fat, which may have certain influence on the value of carcinoembryonic antigen, therefore, we should keep a light diet before the examination, avoid eating after 8 o’clock in the evening of the day before the examination, and pay attention to resting, and we can’t drink water or eat anything on the day of the examination.