Under certain circumstances, a physician will need to make a case-by-case assessment to determine whether a woman's environmental exposure or her own medical condition warrants her to interrupt or stop breastfeeding.

Breastfeeding is NOT advisable if one or more of the following conditions is true:

An infant diagnosed with galactosemia, a rare genetic metabolic disorder
The infant whose mother:
Has been infected with the human immunodeficiency virus (HIV)
Is taking antiretroviral medications
Has untreated, active tuberculosis
Is infected with human T-cell lymphotropic virus type I or type II
Is using or is dependent upon an illicit drug
Is taking prescribed cancer chemotherapy agents, such as antimetabolites that interfere with DNA replication and cell division
Is undergoing radiation therapies; however, such nuclear medicine therapies require only a temporary interruption in breastfeeding