The Department of Health is warning a no-deal Brexit could have a severe impact on the health service.
It has told the health watchdog to be prepared for any adverse impacts.
On July 26, Jim Breslin, the secretary-general of the Department of Health, wrote to Phelim Quinn, the chief executive of Hiqa.
In a letter released under the Freedom of Information Act, he urged the watchdog to continue to take all necessary actions to ensure that areas of the health sector under its remit are prepared for Brexit.
Mr Breslin said a no-deal Brexit is a "very real possibility" and contingency planning must continue.
He insisted the Irish and British governments want to ensure there is minimum disruption to health services between the two states.
He said work is ongoing to ensure the supply of medicines and medical devices is protected.
The secretary-general said the agency must ensure it continues to be able to operate in full compliance with all legislative and regulatory requirements, particularly regarding services or products sourced in or through the UK.
Mr Breslin stressed the need to prepare a communications strategy to ensure service-users are aware of any possible impacts of a no-deal Brexit.