A trend surrounding an unregistered weight-loss drug has triggered a health alert after several people in Victoria were hospitalised with liver damage.

Since January, six cases of acute liver injury were recorded in Victoria among users of an unapproved peptide product, labelled as retatrutide or 'reta'.

'These products have been purchased online, through friends and through social media accounts,' Victoria's Chief Health Officer Dr Caroline McElnay said on Friday. 

'Retatrutide is an experimental drug not approved for sale as a safe medical product in Australia.

'It is marketed widely online for muscle growth, fat loss, recovery and anti-ageing.

'Investigations are ongoing; however, it is believed similar cases may have been reported in some other Australian jurisdictions.'

The alarming warning comes as a young woman has described how her bid to lose weight using the drug ended in a life-threatening medical ordeal.

Megan Hancocks, 32, became interested in the peptide after seeing it on social media but couldn't access it through legitimate means.

During a routine beauty appointment late last year, Ms Hancocks said she was offered off-market peptides sourced from a Chinese manufacturer, available for cash. 

She said she had bought a vial labelled retatrutide, along with another peptide commonly used for skin treatments.

'I was quite small looking back now, but obviously your mind tells you otherwise,' she told ABC News.

She took her first dose on Christmas Eve, followed by another just days later.

But, within a week, Ms Hancocks was rushed to the Royal Melbourne Hospital with acute liver failure.

Her symptoms included severe jaundice including a yellow colour to her eyes, nausea and vomiting, extreme fatigue, stomach swelling and debilitating constipation.

Doctors treated her for about a month and considered the possibility of a liver transplant, but her condition stabilised before the procedure was needed.

After six months, she remains on steroids to repair her liver, has been repeatedly hospitalised, is unable to work and lives at home with her mother.

'When I look in the mirror I don't see the same person anymore and that's been really hard,' Ms Hancocks told ABC News. 

The Therapeutic Goods Administration has also issued a warning, urging Australians to avoid importing and using unapproved peptide products promoted online.

TGA chief medical adviser Professor Robyn Langham said one of the biggest dangers is not knowing what is actually inside the vial.

'There is no way of knowing how much of the peptide is in there, whether the contents are sterile or whether there are other contaminants or toxins in there that you risk administering to yourself,' she said.

'Unmarked vials, code‑only labels, or missing ingredient and dosing information are major red flags.'

Royal Australian College of General Practitioners president Dr Michael Wright supports the TGA's action.

'There really could be risk for patients if they're provided, particularly without medical supervision,' he told newsGP.