Routine blood tests may not detect cancer. Routine blood test only includes blood routine and liver and kidney function tests, which can only find out whether there is anemia and abnormal liver and kidney function. For cancer patients, these indicators may also be normal. In addition, there are also blood tests for tumor markers, which may not be included in the routine blood test, and even if tumor markers are included, it is not possible to diagnose cancer based on the results of tumor markers alone. Usually, other imaging tests, gastroscopy and colonoscopy are needed to diagnose whether there is cancer. In addition, pathological examinations, such as gastroscopy, colonoscopy, or other cytology tests, biopsy, etc., are needed to confirm whether cancer is present or not.