An 81-year-old patient is unable to manage her diabetes effectively. What defining characteristic may indicate poor glycemic control?

A blood sugar level of 545 mg/dL is a clear indication of poor glycemic control in a patient with diabetes. Generally, normal fasting blood sugar levels are typically between 70 and 100 mg/dL, and postprandial (after meals) levels should generally be less than 180 mg/dL. A reading of 545 mg/dL signifies severe hyperglycemia, which can lead to numerous complications including diabetic ketoacidosis or hyperglycemic hyperosmolar state if not addressed promptly. This level is well above the threshold for diagnosis of diabetes and suggests that the patient's management regimen is insufficient, whether it be due to medication adherence, dietary control, or other factors.

In contrast, while elevated triglyceride levels can be associated with diabetes and may reflect poor metabolic control, they do not directly indicate an acute issue with glucose management. Lower extremity edema can occur for various reasons, including heart failure or renal issues, and is not specifically tied to glycemic control. Skin infections are common in individuals with poorly controlled diabetes, but a blood sugar level provides a more direct and quantifiable measure of glycemic control. Thus, the elevated blood sugar level is the most definitive indicator in this scenario.