Robert Flynn (43) was already under a suspended sentence when he went to the hospital in west Dublin and began threatening staff and spitting at patients and gardai.
The case against him was adjourned when he admitted public order offences at Blanchardstown District Court.
Flynn, of Ashington Rise, Cabra, pleaded guilty to public drunkenness and causing a breach of the peace at James Connolly Memorial Hospital, Blanchardstown, on June 29 last.
He also admitted a separate charge of intoxication at Oliver Plunkett's GAA grounds, Glengariff Road, Navan Road, on May 14.
The court heard gardai were called to the hospital at 7pm after receiving a report that the defendant was threatening staff members and patients.
On arriving, they found the defendant in a highly intoxicated state.
He was spitting in the direction of gardai and patients. He was arrested and brought to Blanchardstown Garda Station.
In the earlier incident, gardai arrived at the GAA grounds at 10.46pm. Two staff members said the defendant was extremely intoxicated and he was arrested for his own safety.
Judge O'Donnell adjourned the case for the attention of the judge who had imposed the suspended sentence.