It carried out an unannounced inspection in June and discovered poor hygiene standards in various areas.
HIQA inspectors visited Letterkenny on June 18th.
They found a number of areas of concern that warranted an immediate high risk finding.
There was dust in many places, and some floors were not cleaned to an acceptable standard.
There were also brown stains in some toilets, red stains on some patient equipment, window leaks and flaky paint.
A follow up inspection found no significant improvement.
Meanwhile Regional Health West Forum member Gerry McMonagle is calling for an investigation into the findings: