Antonyms for the phrase "are alert" can vary depending on the context of its usage. The word "alert" can have different synonyms such as watchful, cautious, attentive amongst others. The opposite of being alert, or watchful, is being oblivious or careless. Words such as unobservant, inattentive, and distracted come to mind. If it's in a medical context, the opposite of alert would be unconscious or comatose. In contrast, the opposite of being cautious or guarded may be reckless, impulsive, or daredevil. In conclusion, antonyms for "are alert" differ depending on the context in which it's used.