The High Court in Glasgow heard that Brian Docherty's car ploughed into friends Elizabeth McGuiness and Barbara McCready as they walked from a church service in Motherwell, Lanarkshire, in June last year.
Miss McGuiness, 63, died and Mrs McCready, 64, was left seriously injured.
Docherty, from Uddingston, Lanarkshire, should not have been on the road. He should have told DVLA of his diabetic condition.
The 45-year-old also had a poor history of taking medication to control his diabetes.
Jailing him judge Lady Stacey said: "Nothing I can say or indeed anything you can say or do can lessen the grief for the family of Miss McGuiness. You will have to live with the knowledge of causing the death of one woman and serious injury to another."
Lady Stacey also banned Docherty from driving for 10 years.