The HSE spent 568 million on agency staff in 2021, and 543 million in the first 11 months of last year.
Across the 23 months, almost 240 million was spent on nursing staff, 200 million on management and administrative staff, and over 101 million on paramedics.
Beaumont Hospital consultant Bill Tormey says many medical staff are leaving the country, for several reasons.
"A lack of morale - number one. Number two - that people are not being paid the going rate."
The HSE says the availability of health staff continues to be a challenge, not only in Ireland but around the world.
Where there are shortfalls, agency staff are employed.
The HSE says in a number of instances in recent times, it has been unable to fill a vacancy, even with agency staff.
Reporting by Eoghan Murphy.