Among adults aged 65 years, the prevalence of diagnosed diabetes was 15.3%, representing 5.4 million individuals in the U.S. The prevalence of undiagnosed diabetes was 6.9% or 2.4 million individuals. Elderly individuals with middle age– onset diabetes had a much greater burden of microvascular disease but have a similar burden of macrovascular disease compared with individuals with elderly onset diabetes. Elderly individuals with middle age– onset diabetes had substantially worse glycemic control compared with either elderly onset.