According to a study that estimated life expectancy of type 2 diabetic patients in the US, males and females diagnosed at 51-55 years had a life expectancy of 80 years and 84 years, respectively. Diabetes UK estimates that life expectancy is reduced by 10 years in type 2 diabetes and by 20 years in type 1 diabetes compared to a non-diabetic person. Mortality was associated with amputation and reduced visual acuity in type 1 diabetes, whereas it was related to complications in the heart, kidneys, nerves, and eyes in type 2 diabetes.
Reference:
Diabetes Journals: https://diabetes.diabetesjournals.org/content/69/Supplement_1/1401-P.abstract
Diabetes: https://www.diabetes.co.uk/diabetes-life-expectancy.html
Diabetes Journals: https://care.diabetesjournals.org/content/28/3/617