The association between health literacy and glycemic control that we observed is significant from a clinical and public health perspective. The proportion of patients with tight glycemic control vs poor control is routinely used as a quality-of-care indicator for diabetes.29 Glycosylated hemoglobin is an objective clinical end point that has been linked to health care use and costs30 and disabling and life-threatening conditions.31,32 Studies have demonstrated that there is a curvilinear relationship between HbA1c and microvascular complications and that a decrease in HbA1c of 1 percentage point (from 9.0% to 8.1%, for example) results in a halving of the risk of retinopathy.31- 33 Consistent with this body of research, our study showed that the worse glycemic control experienced by patients with inadequate health literacy was reflected in a higher prevalence of retinopathy. When compared with patients with adequate health literacy, patients with inadequate health literacy had 2 times the odds of having retinopathy, even after adjustment for patient sociodemographics, diabetes education, treatment regimen, and duration of diabetes.