Limited access to health care is associated with adverse outcomes, but few studies have examined its effect on glycemic control in minority populations. Our observational cross-sectional study examined whether differences in health care access affected hemoglobin A1c (HbA1c) levels in 605 patients with diabetes (56% women; 89% African American; average age, 50 years; 95% with type 2 diabetes) initially treated at a municipal diabetes clinic. Patients who had difficulty obtaining care had higher A1c levels (9.4% vs. 8.7%; p=0.001), as did patients who used acute care facilities (9.5%; p<0.001) or who had no usual source of care (10.3%; p<0.001) compared with those who sought care at doctors' offices or clinics (8.6%). In adjusted analyses, HbA1c was higher in persons who gave a history of trouble obtaining medical care (0.57%; p=0.04), among persons who primarily used an acute care facility to receive their health care (0.49%; p=0.047), and in patients who reported not having a usual source of care (1.08%; p=0.009). Policy decisions for improving diabetes outcomes should target barriers to health care access and focus on developing programs to help high-risk populations maintain a regular place of health care.