CEA Blood Test: What It Tests & Normal Levels

The CEA blood test is ordered to identify circulating levels of carcinoembryonic antigen (CEA), which is a protein produced when there is rapid growth of digestive cells. This can occur during fetal development or with colorectal cancer. 

People without any gastrointestinal symptoms or smokers can present with elevated levels of CEA. Therefore, it is important for the doctor to evaluate the results of other tests to understand why levels may be increased. 

CEA tests can be used to monitor patients being treated for colorectal cancer. CEA levels will typically return to more normal levels about 6 weeks after surgery, for example. This protein can also be used to evaluate pancreatic and liver disease, and even breast dysplasia. 

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What it tests

CEA testing is usually ordered to aid in the diagnosis of colorectal cancer. However, because it is not a specific test, other tests are needed to confirm a diagnosis. CEA is most used to monitor a patient’s response to chemotherapy.

In addition to being useful for gastrointestinal cancers, CEA levels can also be elevated with other health conditions, such as: 

  • Pancreatic cancer 
  • Lung cancer
  • Liver cancer
  • Irritable bowel syndrome
  • Thyroid cancer
  • Pancreatitis
  • Lung infections
  • Chronic smoking
  • Benign breast lumps (non-cancerous nodules or cysts) 

Given that many health conditions can cause elevated CEA levels, the doctor will often order this test alongside other exams to pinpoint a diagnosis. 

Normal levels

Reference ranges for CEA levels will vary from lab to lab, which is why repeat CEA testing should always be done at the same lab. This will allow for accurate evaluation for the patient’s current health status.  

In addition, it is also important for doctors to factor in whether the patient is a smoker or not, as reference values will be different. Normal CEA levels are considered to be:

  • Up to 5.0 ng/mL in smokers 
  • Up to 3.0 ng/mL in non-smokers.

CEA levels may be slightly increased in patients without any disease processes, however. Levels that are 5 times above normal levels, on the other hand, can be a sign of cancer with possible metastasis. Therefore, it is important to interpret results with other tests to reach a diagnosis.