About 60,000 people self-harmed last year, mental health experts have said.
The Irish Association of Suicidology (IAS) said casualty units recorded 12,000 cases but estimated that the real figure could be five times as high.
The campaign group's conference in Sligo was also told that people suffering deliberate self-harm - especially repeat patients - were treated poorly in hospital compared with others with purely physical conditions.
Oxford University Professor Keith Hawton said hospital staff tended to view patients who injured themselves in a poor light.
He said there was clear evidence that brief psychological therapy can help prevent repeat self-harm and reduce levels of depression, hopelessness and suicidal thoughts.
"Furthermore, hospital staff's knowledge about deliberate self-harm patients and their risk of suicide is often limited," he said.
"Training programmes have been shown to benefit knowledge and attitudes."
The professor of psychiatry and director of the centre for suicide research at Oxford said the findings were revealed in a worldwide systematic review of deliberate self-harm services.