What HbA1c level is most consistent with poorly controlled diabetes?

HbA1c (glycated hemoglobin) reflects average blood glucose over approximately 2-3 months. Targets and interpretations: <5.7% = normal; 5.7-6.4% = prediabetes; ≥6.5% = diabetes diagnosis threshold; <7.0% = well-controlled diabetes (ADA treatment target); 7.0-7.9% = moderately uncontrolled; ≥8.0% = poorly controlled diabetes, significantly increasing risks of microvascular and macrovascular complications. For dental implications, HbA1c ≥8.0% indicates increased risk of delayed wound healing, infection, and periodontal disease progression. The periodontal classification uses HbA1c ≥7.0% as the modifier threshold for Grade C periodontitis. The answer d represents the consistently recognized threshold for 'poorly controlled' diabetes.