Antrim Area Hospital and Causeway hospitals are both under pressure with Antrim being described as "extreme pressure" and Causeway as "significant pressure".
A Northern Trust spokesperson said "There are significant numbers of extremely sick patients in our Emergency Departments.
"Both hospitals are over capacity and we are doing all we can to secure safe discharges in order to admit patients from the Emergency Dept.
"Our staff is working extremely hard but you may experience a long wait. Please be assured we are seeing patients in clinical priority."
