Health chiefs said discharging patients overnight was not NHS policy in Forth Valley.
It comes as figures revealed almost 240,000 people were sent home from hospitals in England between 11 p.m. and 6 a.m. last year.
The head of the NHS has now launched an inquiry into the late-night discharges.
But health bosses in Forth Valley said it did not routinely send patients home during the night.
A spokeswoman for the health board said: “Patients sometimes choose to discharge themselves from hospital and may be discharged during the night where arrangements have been made with them and their families to return home during this period. This could include maternity patients and patients who had been undergoing assessment in our clinical and assessment units.”
Figures received under a Freedom of Information request, showed that of the 100 health trusts in England which responded, 239,233 patients had been discharged overnight.
There are concerns that some elderly patients are being sent home to empty houses.
Sir Bruce Keogh, medical director of the NHS, said: “I am concerned to hear that some patients may be being discharged unnecessarily late.
“Patients should only be discharged when it’s clinically appropriate, safe and convenient for them and their families. It is simply not fair to be sending people home late at night. We will look at this.”