Around 44,000 unused appointments between July and September 2009 cost the NHS in Scotland an average of £112 ($169) each, totalling £5m ($7.5m), a new report has found.
According to an Audit Scotland report, about one in ten patients did not attend their first outpatient appointment.
People who do not attend their appointments can now be put back to the end of the queue or taken off the waiting list and referred back to their GP, according to new guidelines.
The report also said that some boards may put a patient to the end of the waiting list after the first time they fail to attend an appointment, the report said.
Auditor General for Scotland Robert Black said that patients have responsibilities to attend appointments.
"Under the new guidance, patients who fail to attend may be taken off the waiting list and referred back to their GP and it's crucial that the NHS tells patients this," Black said.
"The NHS also needs to give people enough notice of appointments and make sure that they get information about their appointment in a way they can understand so that they are in a good position to be able to attend."