The TV presenter and daughter of musician Bob Geldof had been a heroin addict and was taking the substitute drug methadone for two-and-a-half years before her death, but had apparently begun using heroin again.
The 25-year-old was found by her husband, Tom Cohen, slumped in a spare room of the home they shared in Wrotham, Kent, on April 7. He had been away with the older of their two sons, Astala, leaving Geldof at home with their 11-month old son, Phaedra.
Geldof was pronounced dead at the scene.
Police later found 6.9 grams of heroin in the house. A syringe containing the fatal dose was discovered hidden in a box of candy next to the bed.
Cohen told the inquest looking into Geldof's death that his wife had begun using the drug again earlier this year in February, according to the BBC.
He said he witnessed her flushing drugs down the toilet but was unaware of other drugs in the house until they were found by police.
Cohen added that his wife had taken weekly drug tests since seeking treatment for her addiction two years ago, but he now believes that she lied about the tests being negative.
According to the BBC, pathologist Peter Jerreat said the levels of heroin in Geldof's body were in a "fatal range." Traces of codeine, methadone and morphine were also found in her blood. The pathologist also noted that puncture wounds were found on Geldof's body on her elbows, wrists and thumbs.
"It's said that the death of Peaches Geldof-Cohen is history repeating itself but this not entirely so," coroner Roger Hatch said at the inquest, according to the BBC.
Geldof's mother, Paula Yates, died of a heroin overdose at the age of 41 when Peaches was 11 years old.
"By November last year, she had ceased to take heroin as a result of the considerable treatment and counseling that she had received," Hatch said. "This was a significant achievement for her but, for reasons we will never know, prior to her death she returned to taking heroin."