What is the normal reference range for carcinoembryonic antigen (CEA) on the test report?

Carcinoembryonic antigen (CEA) often reflects the presence of malignant tumors. Moreover, CEA testing can help differentiate between benign and malignant tumors. As the number of cancer patients continues to rise, CEA testing is increasingly incorporated into routine diagnostic evaluations. Elevated CEA levels beyond the normal reference range warrant clinical attention. So, what exactly is the normal CEA value? Let’s explore this further.

What is the normal CEA value on a laboratory report?

CEA serves as a biomarker capable of reflecting the presence of various tumors and is clinically useful for evaluating treatment response, monitoring disease progression, and estimating prognosis in colorectal, breast, and lung cancers. However, its specificity and sensitivity are relatively low, limiting its utility in early tumor detection. CEA is normally produced by embryonic tissues, and its concentration in the human body gradually declines—and may even become undetectable—after birth.

CEA, short for carcinoembryonic antigen, is a broad-spectrum tumor marker first identified in colorectal cancer tissue and fetal intestinal tissue—hence its name. It is predominantly expressed in malignancies arising from endoderm-derived digestive organs, as well as in normal fetal gastrointestinal tissues. Small amounts are also present in the serum of healthy adults and may reflect the presence of multiple tumor types.

CEA was initially discovered in both colorectal carcinoma and fetal intestinal tissue, leading to its designation as “carcinoembryonic antigen.” It serves as an auxiliary diagnostic indicator for gastrointestinal malignancies. The normal reference value is ≤5 ng/mL. Elevated CEA levels are commonly observed in colorectal cancer, pancreatic cancer, gastric cancer, small-cell lung cancer, breast cancer, and medullary thyroid carcinoma.

However, CEA levels may also increase in non-malignant conditions—including smoking, pregnancy, cardiovascular disease, diabetes, and nonspecific colitis—occurring in 15–53% of affected individuals. Therefore, CEA is not a specific marker for malignancy and holds only adjunctive diagnostic value. Furthermore, serum CEA concentration correlates significantly with the stage of colorectal cancer: more advanced disease typically corresponds to higher CEA levels. In 97% of healthy adults, serum CEA remains below 2.5 ng/mL.

CEA elevation occurs in 45–80% of patients with primary colorectal cancer. High positivity rates (typically 50–70%) are also seen in other malignancies, including pancreatic adenocarcinoma, cholangiocarcinoma, gastric cancer, esophageal adenocarcinoma, lung cancer, breast cancer, and urological tumors. In benign conditions—such as colonic polyps, ulcerative colitis, pancreatitis, and alcoholic cirrhosis—CEA may be mildly elevated, though levels generally remain far lower than those observed in malignancy (usually <20 ng/mL). A CEA level exceeding 20 ng/mL strongly suggests the presence of a gastrointestinal malignancy.

We hope the above information has been helpful. Wishing you good health and happiness!