There is no exact value for how high CA153 is dangerous. Normal people’s serum CA153 is usually less than 30U/mL, once found that CA153 is elevated should be taken seriously, and further examination is needed to clarify the diagnosis. CA153 is a kind of tumor marker. In general, if the tumor marker exceeds the normal range by more than 2 times, it is necessary to consider whether there is a possibility of malignant tumors, such as breast cancer patients’ CA153 can be significantly elevated. CA153 is closely related to breast cancer and has important auxiliary diagnostic value for breast cancer. When the level of serum CA153 is higher than 100U/mL, it often suggests the possibility of metastasis. When metastasis occurs in breast cancer, CA153 sensitivity can reach 60~80%. For patients with stage II and III breast cancer, dynamic monitoring of CA153 can help early detection of metastasis and recurrence. Elevated serum CA153 is not only related to breast cancer, but also may be related to lung cancer, intestinal cancer, etc. In addition, non-malignant neoplastic diseases such as breast, liver, etc. may also show slight elevation of CA153. If CA153 is found to be elevated, it is recommended to consult a doctor for further examination and diagnosis in order to avoid delaying the condition.