Corey Wood, 22, was told to return to the Warrnambool hospital the next day. Instead he went home and stabbed his brother with a 30cm-long blade before grabbing the dog by the throat and threatening to kill it.

"You've stabbed your brother and looks like he is going to die," Wood's mother told him after the attack on October 15, 2018.

Wood replied: "I hope he does".

The brother was left blue, gasping for breath and going in and out of consciousness but survived after emergency surgery.

Wood pleaded guilty to offences including aggravated burglary, recklessly causing serious injury and assault.

He had been mentally unwell and used drugs, and accused his brother of conspiring with the dog against him before launching an attack with two knives.

After being arrested and taken to the local police cells, Wood beat up another prisoner.

Being turned away from South West Healthcare was "a particularly sad scenario" with significant repercussions, Wood's legal aid lawyer Morgan Adams told the County Court of Victoria on Tuesday.

A magistrate had ordered the young man go for a mental health assessment after being granted bail for other offences.

"Unfortunately he was sent away and told to come back the next day," Mr Adams said.

The mishap ended in an investigation and magistrates no longer made these kinds of orders, the lawyer added.

Wood spent 334 days in custody before being bailed to a rehabilitation centre.

He now understood drug use was extremely damaging for his mental health, Mr Adams said.

Judge Gerard Mullaly indicated he was prepared to sentence Wood to time already served followed by a strict community correction order.

He is due to be sentenced on July 1.

Australian Associated Press