Carcinoembryonic antigen (CEA) 0.51 is normal, which means that it is unlikely that the person tested has a disease, but it cannot be ruled out completely. Carcinoembryonic antigen is a tumor marker that is often detected in blood, its normal value range is usually less than 5, if this indicator is more than 5, it is usually considered that the patient may suffer from oncological diseases, such as gastric cancer, lung cancer, etc., or some non-oncological diseases, such as gastroenteritis, cervicitis, etc. Therefore, the value of 0.51 is within the normal range, which means that the patient may suffer from the disease. Therefore, the value of 0.51 is within the normal range, indicating that the possibility of the above diseases is relatively small, which is a good situation. However, it should be noted that normal carcinoembryonic antigen index cannot completely exclude the possibility of suffering from the disease, and once there are clinical symptoms, one should consult the doctor in time to do relevant examination to avoid missing diagnosis.