He said he was more upset than the relatives after Mrs Kathleen Wagstaff, 81, died while he was visiting her home after she complained of chest pains. His counsel, Nicola Davies QC, asked why there was an error on the death certification. He said: "I was quite upset, I don't think I was quite clear in my own mind when I completed this document."
The court was told Dr Shipman had wrongly written that a neighbour was present as well as himself when Mrs Wagstaff died. He added: "Under normal circumstances I don't feel I would have entered the neighbour on it [the certificate] at all.
"If you'd asked me about these facts on the Monday or Tuesday after she died I don't think I would have given you a sensible answer. This was one of the few times I was possibly more upset than the relatives."
Dr Shipman, 53, had been standing in the box on the 30th day of the trial. He apologised to the jury and sat down, burying his head in his hands.
He said he had been called to Mrs Wagstaff's home in Rock Gardens, Hyde, after a phone call from the 81-year-old to his surgery on 9 December 1997.
Dr Shipman said Mrs Wagstaff complained of chest pains and looked grey. He made a "presumptive diagnosis of coronary thrombosis" and "looked around for a phone to call for an ambulance". He said he saw Mrs Wagstaff sitting upright in the chair with her mouth open.
Ms Davies asked: "Did you administer morphine or diamorphine?" Dr Shipman replied: "No, I did not." Then she asked: "Did you murder Laura Wagstaff?" Dr Shipman said: "No, I did not."
The trial continues today.