Improving the quality of primary care may reduce avoidable hospital admissions. Avoidable admissions for conditions such as diabetes are used as a quality metric in the Health Care Quality Indicators of the Organization for Economic Cooperation and Development (OECD). Using the OECD indicators, we compared avoidable admission rates and spending for diabetes-related complications in Japan, Singapore, Hong Kong, and rural and peri-urban Beijing, China, in the period 2008–14. We found that spending on diabetes-related avoidable hospital admissions was substantial and increased from 2006 to 2014. Annual medical expenditures for people with an avoidable admission were six to twenty times those for people without an avoidable admission. In all of our study sites, when we controlled for severity, we found that people with more outpatient visits in a given year were less likely to experience an avoidable admission in the following year, which implies that primary care management of diabetes has the potential to improve quality and achieve cost savings. Effective policies to reduce avoidable admissions merit investigation.