Victorian health authorities have issued an urgent warning after six Australians were hospitalised with serious liver damage linked to an unapproved weight-loss product known as Retatrutide.

The experimental drug, which is not approved for use in Australia, has been promoted online as a fast-track solution for weight loss and fitness goals.

Health officials say several patients suffered acute liver toxicity, with some requiring hospital treatment after experiencing symptoms including jaundice, abdominal pain and severe fatigue.

Experts believe contaminated or counterfeit products sold through social media, online platforms and unofficial suppliers may be responsible for the illnesses.

Authorities are urging people to avoid any products labelled Retatrutide, Reta, R-10 or R-20 and to seek immediate medical attention if they experience unusual symptoms after use.

Investigations are continuing as health regulators warn that unapproved peptide products can pose life-threatening risks and have not been assessed for safety or effectiveness.