An investigation has been launched into the death of a baby in Australia who died after being sent home from two Perth hospitals and a doctor's surgery over three days.

Seven-month-old Malakai Matui Paraone, whose dad is from New Zealand, died from suspected meningococcal in Princess Margaret Hospital in Perth on Friday, leaving his parents wanting answers as to why the system failed their son.

In a Facebook post, Ms Thompson has mourned the loss of Malakai, saying the "pain will never go away".

"I still wake up for ur feeds and it's just so strange not feeding you, hearing you, cuddling you, miss you my boy. Just wish i had u in my arms again. It's not fair! (sic)"

Malakai was taken to Midland Hospital a week ago, with his mother Nicole Thompson saying he couldn't move the right side of his body, had joint pain, fever and a rash.

He was given pain relief and sent home.

The next day, Ms Thompson called an ambulance and Malakai was taken to Princess Margaret Hospital because his condition had got worse.

Ms Thompson was told Malakai had an elbow problem and was teething - she was given pain relief and sent home.

It was only on his third visit to Princess Margaret on Thursday that hospital staff realised Malakai needed intensive care - but by then it was too late.

Malakai died two days later.

Western Australia Health Minister John Day's now ordered an investigation by the morbidity and mortality review committee to look into both hospitals and the Rockingham clinic where Malakai was also taken.

He also apologised to the family, Perth Now reports.

"I am very sorry as a parent myself and now as a grandparent of a three-year-old that there has been this outcome," he said.

A spokesperson for Princess Margaret Hospital said they didn't comment on individual cases, but the death was being investigated by the coroner.

A GoFundMe page was set up to help pay for funeral costs has already exceeded its goal of $15,000 and is currently at more than $17,000.

Newshub.