Background: China is facing the challenges of the increasing burden of diabetes and obesity; the prevalence and numbers of diabetes patients with obesity or overweight are still unclear. Methods: Nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS) were used to estimate the prevalence of diabetes patients with elevated BMI, the recommendation rate for antidiabetic medication, the blood glucose control rate, and the corresponding population size. Results: The prevalence of diabetes patients with elevated BMI was 9.18% (95% CI: 7.88, 10.68; representing 31.54 million) in China. More than half of people with diabetes had elevated BMI (overweight or obesity). Among the participants who were not taking antidiabetic medication, 26.15% (95% CI: 18.00, 36.36; representing 3.79 million) were recommended for antidiabetic medication by the 2020 CDS guideline. There were 24.62% (95% CI: 16.88, 34.45; representing 3.64 million) patients, representing 11.13 (95% CI: 9.86, 12.41) million people, with diabetes combined with elevated BMI, taking antidiabetic medication, and still above the goal blood glucose. Conclusions: Our results indicate that diabetes combined with elevated BMI has become a major public health problem in China in people over 45 years of age. Moreover, the prevalence and population size of women are higher than those of men, and the prevalence of people over 65 years old is slightly lower than that of elderly people aged 45–65. The recommended rate of antidiabetic medication and the control rate of blood glucose were high, and prevention and treatment strategies for diabetes combined with elevated BMI are needed.