Standard blood glucose targets are lower than HbA1c goals require

A recent study determined the pre- and postprandial blood glucose levels that should be targeted to reach a specific HbA1c goal in patients with type 1 or type 2 diabetes.

Researchers used data from participants in the hemoglobin A1c-Derived Average Glucose (ADAG) study, a multicenter observational study that included continuous glucose monitoring and self-monitoring blood glucose (SMBG) readings. Of the 470 patients included in this analysis, 237 had type 1 diabetes and 147 had type 2 diabetes. Their average fasting, premeal, postmeal and bedtime blood glucose readings were compared to their HbA1c levels.

Results were published online Feb. 10 by Diabetes Care.

The researchers found that an HbA1c of 5.5% to 6.49% was associated with an average fasting glucose of 122 mg/dL (95% CI, 117 to 127 mg/dL), an HbA1c of 6.5% to 6.99% was associated with 142 mg/dL fasting (95% CI, 135 to 150 mg/dL), an HbA1c of 7.5% to 7.99% was associated with 167 mg/dL (95% CI, 157 to 177 mg/dL), and an HbA1c of 8.0% to 8.5% was associated with 178 mg/dL (95% CI, 164 to 192 mg/dL). Postmeal average glucose was 139 mg/dL for patients with an HbA1c of 6.5% to 6.99% and 152 mg/dL for those with an HbA1c of 7.0% to 7.49%. Bedtime glucose was 153 mg/dL and 177 mg/dL in those HbA1c categories, respectively. Type 1 and type 2 diabetes patients were analyzed separately, but because their results were fairly similar, they were combined in the final analysis. (To convert glucose values to approximate equivalents in mmol/L, divide the mg/dL value by 18.)

The results show that “currently published SMBG targets are not consistent with the empirical data,” the authors concluded. They noted that most SMBG targets are based on expert opinion or extrapolations from average daily glucose levels. Current recommendations typically target a fasting glucose of under 100 to 115 mg/dL, the authors noted, but this study shows that patients with an HbA1c of 5.5% to 6.49% have a fasting glucose of 122 mg/dL. For postprandial glucose, this study provides more specific numbers than the usual target of less than 180 mg/dL, they said.

Glucose monitoring schedules and goals are complex issues that should be decided based on individual factors, but these data may help patients and clinicians choose appropriate SMBG goals to achieve their selected HbA1c targets, the study authors said. They encouraged professional societies, clinicians and patients to consider these data in their future decision-making.