Harry Lamont, 46, supplied the heroin substitute methadone to Natalie Fry in a flat in Scotstoun, Glasgow, in March 2012.
The High Court in Edinburgh heard how Ms Fry lost her life after taking the narcotic.
However, Lamont then gave heroin to another woman called Sharon Gibb at the same flat in April 2012.
He injected her with the drug and she also died.
Lamont, of Saltmarket, Glasgow, originally faced two charges of culpable homicide.
But following a trial at the High Court in Glasgow last month, a jury convicted Lamont on two charges of reckless conduct.
Judge Lord Carloway deferred sentence on Lamont until yesterday in order to obtain reports about Lamont's character.
On Wednesday, defence solicitor advocate John Scott QC told the court that his client suffered from learning difficulties.
Passing sentence, Lord Carloway referred to a report that had been written for the court by a social worker.
He added: "The Social Enquiry Report shows that you have little remorse for the deaths of these girls."