There are "suggestions" that an 18-year-old student told friends she had taken the drug ketamine shortly before her death, an inquest has heard.
Cardiff University student Megan Pollitt, from Rugby, Warwickshire, died in hospital on 16 November after collapsing at a halls of residence.
The inquest heard Ms Pollitt's death is "possibly related to a drugs overdose".
The results of a post-mortem examination is pending further investigation.
Senior coroner for South Wales Central Graham Hughes said: "There is reason to suspect her death was unnatural and possibly related to a drugs overdose or toxicity."
The first-year law student was found collapsed in the doorway of her flat in the Talybont halls of residence in Cardiff on 14 November by student friends, the hearing was told.
Ms Pollitt later died at the University of Wales Hospital in Cardiff.
Her family said in a tribute that she had a "bright, beautiful smile and positive energy".
The inquest hearing date has been given as 18 January 2022.