The Southern Health and Social Care Trust, which includes the Dungannon District, has spent almost £5million on taxis and buses for patients in the last five years.
The bill has risen by £61,815 in the past year, from £890,484 in 2014 to £952,299.
The annual bill had been dropping since 2010, from £1.2m, but is still one of the highest in the North.
The figures were revealed this week by the Department of Health at the Northern Ireland Assembly.
The South Eastern Trust racked up the highest cost at £1m last year, while the Western Health and Social Trust ran up the smallest transport bill at £739,455.
A spokesperson for the Department of Health said the taxis were used for a variety of reasons.
Most of the expenditure was incurred on the transport of vulnerable patients and clients, particularly children in care and adults with a physical or learning disability.
“The use of taxis by Health and Social Care Trusts is planned and monitored”, added the spokesperson.
The bill has angered health service unions who claim the money could be better invested in front line staff and improved services.
Joe McCusker, regional organiser with Unison, said: “We certainly are shocked and alarmed that so much money is being spent. There needs to be an examination into whether or not these costs are viable and justified.
Local trusts have had to pay transport and accommodation costs for patients transferred to hospitals in the Republic for non-emergency operations in a bid to cut waiting times or because procedures could not be carried out in Northern Ireland, according to health department officials.
Flights, taxis and hotels have cost the Belfast Health and Social Care Trust £3,001,049 since 2008.