Victoria Arnott stopped the emergency vehicle en route to the woman's home to pick up equipment that she needed, a misconduct hearing was told yesterday.
The former Scottish Ambulance Service worker, who was on duty, agreed she had visited a store without seeking authorisation from the ambulance control centre in Fife on July 4 last year.
Ms Arnott denied misusing the vehicle for personal purposes when she appeared before the conduct and competence committee of the Health and Care Professions Council's (HCPC) .
A three-member panel heard Ms Arnott, who joined the ambulance service in 1999, had been allocated a doctor's urgent call to attend the home of a depressed and suicidal woman and take her to hospital.
Rowena Rix, representing the HCPC, said: "On that same date the control room supervisor reported to the duty shift manager that there had been a delay in Ms Arnott's crew responding to this call.
"She admitted she had stopped the ambulance en route to the urgent call in order to undertake some personal shopping."
Ms Rix said there had been a delay in the treatment of the patient and that, though there was no suggestion the patient was hurt as a result, the paramedic's actions could have caused harm.
She said the paramedic had acted unprofessionally and had put her own interests before those of the patient
Witness Iain Morgan, who was the east ambulance control centre duty shift manager at the time, told the panel that investigations showed the ambulance had deviated from its route for around seven minutes.
He said: "I spoke to Victoria and she informed me she picked up something to do with her computer.
Ms Rix asked: "In your experience is it ever acceptable to stop en route to an urgent call?"
"No, it's not," Mr Morgan said.
However, Alice Stobart, counsel for Ms Arnott, suggested that there was a procedure for paramedics to stop en route and others had been authorised to do so in the past.
Mr Morgan said: "There isn't any procedure to allow that. I can only say in my experience that's not the case.
"They would not be allowed to do it while they were en route to a call."
The call was at the second lowest level of priority for the ambulance service with a response window of one to four hours, the panel was told.
It had initially been received by the control room at 11.41am and was not allocated to Ms Arnott's crew until 3.35pm.
Ms Stobart said that, given such a window, her client might have expected to know from experience that there was unlikely to be clinical or medical attention necessary.
The hearing is expected to last two days. The panel will rule on whether misconduct has been proved and if so, whether Ms Arnott's fitness to practise is impaired.
The Scottish Ambulance Service said Ms Arnott is no longer an employee.