Brian Docherty ploughed into Elizabeth McGuiness and her friend Barbara McCready as they returned from a church service in Motherwell in June last year.
Docherty should not have been on the road having failed to tell the DVLA of his condition.
The 45-year-old also had a poor history of taking medication to control his Type 2 diabetes.
Docherty yesterday admitted causing the death of Miss McGuiness by dangerous driving and leaving Mrs McCready severely injured.
A judge remanded him in custody at the High Court in Glasgow and he will learn his fate next month.
The court was shown CCTV footage of the carnage Docherty caused. He drove down a one-way road in Muir Street, Motherwell, but then stopped his Vauxhall. A witness said that the accused appeared to be having some kind of fit.
Despite this, Docherty accelerated forcing other drivers to try and dodge him. Miss McGuiness, 63, and Mrs McCready, 64, were hit as they walked to a local cafe.
Docherty, of Uddingston, South Lanarkshire, eventually came to a halt after smashing into nearby railings.
GP records showed Docherty – who had previously been forced to give up his job as a driver – "poorly controlled" his diabetes.
Ali Murray, defending, said Docherty had since given up his licence to police and was also "realistic" in that he expected to face a jail term.