Her husband, Thomas Cohen, told the hearing the television presenter had started using heroin again in February this year.
He said he had witnessed her flushing drugs she had hidden in the loft of their home in Kent down the toilet.
In April the 25-year-old was found slumped on the bed in the spare room by Mr Cohen.
The musician confirmed that he had gone to stay with his parents in south east London with the couple's two sons, Astala, two, and one-year-old Phaedra, and that she had seemed fine when he spoke to her on several occasions over the weekend.
The inquest heard that Mr Cohen's father, Keith, had seen Ms Geldof when he dropped the younger child home to her and she appeared fine, and Mr Cohen said he had last spoken to his wife at 5.40pm on Sunday 6 April.
After failing to get hold of his wife the next day, Mr Cohen and his mother returned to the property with Astala and found Ms Geldof's body, the hearing was told.
The model had been having weekly drugs tests which she had told her husband were negative but, even though he had not seen her take drugs, he became concerned that she might be, the inquest was told.
North West Kent Coroner Roger Hatch said Ms Geldof had been finding it difficult to come off methadone although she was reducing the dosage because she did not want to take it anymore.
Mr Cohen had spoken to his wife about her drugs use and she retrieved heroin from the loft in February this year and flushed it down the toilet, the inquest was told.
Following this, Mr Cohen would check the loft for drugs himself but found nothing, Mr Hatch said.
For reasons we will never know prior to her death, she returned to taking heroin.
Roger Hatch, North West Kent Coroner
But Mr Cohen became aware from police inquiries following her death that drugs were found in the house.
A post-mortem examination carried out at Darenth Valley Hospital found a puncture mark on the front of her right elbow and another at the front of her right thigh.
Old puncture marks were also found on her left thigh, the inquest was told.
Mr Hatch concluded that Ms Geldof's death was drugs-related and that heroin had played a part in her death.
He said that although she had struggled to come off methadone because of her addiction to heroin, by November 2013 Ms Geldof was found to be free of heroin and reducing her methadone.
But a message found on her phone by Mr Cohen in February this year which indicated she was using drugs again, he told the hearing.
Mr Hatch said: "It's said that the death of Peaches Geldof-Cohen is history repeating itself but this not entirely so.
"By November last year she had ceased to take heroin as a result of the considerable treatment and counselling that she had received.
"This was a significant achievement for her but for reasons we will never know prior to her death she returned to taking heroin."