What should the blood glucose level be before meals for individuals with type 2 diabetes mellitus (T2DM) on insulin?

Target Blood Glucose Levels Before Meals for T2DM Patients on Insulin

For patients with type 2 diabetes mellitus on insulin therapy, the recommended preprandial blood glucose target is 80-130 mg/dL (4.4-7.2 mmol/L). 1

Standard Glycemic Targets

• The American Diabetes Association (ADA) recommends a preprandial capillary plasma glucose target of 80-130 mg/dL (4.4-7.2 mmol/L) for most nonpregnant adults with diabetes 1
• This target represents a change from earlier guidelines (pre-2015) that recommended 70-130 mg/dL (3.9-7.2 mmol/L) 1
• The adjustment to raise the lower limit from 70 mg/dL to 80 mg/dL was specifically made to limit overtreatment and provide a safety margin for patients using glucose-lowering medications like insulin 1

Hypoglycemia Prevention and Management

• Blood glucose <70 mg/dL (3.9 mmol/L) is considered clinically important hypoglycemia and requires immediate action 1
• Blood glucose <54 mg/dL (3.0 mmol/L) is defined as Level 2 hypoglycemia, where neuroglycopenic symptoms begin to occur 1
• Patients experiencing hypoglycemia should be treated with 15-20g of glucose, with a repeat check after 15 minutes 1
• If premeal glucose readings are frequently below target, insulin doses should be reduced to prevent hypoglycemia 2

Individualization of Targets Based on Patient Factors

• More stringent targets may be appropriate for selected patients if they can be achieved without significant hypoglycemia 1
• Less stringent targets (90-150 mg/dL or 5.0-8.3 mmol/L) are recommended for older adults, especially those with complex health issues or limited life expectancy 1
• Patients with history of severe hypoglycemia, hypoglycemia unawareness, or limited life expectancy may benefit from higher glycemic targets 1

Insulin Adjustment Algorithm

• If fasting or premeal glucose values are consistently below 80 mg/dL, reduce basal insulin dose by 2 units 1
• For patients with recurrent hypoglycemia, reduce prandial insulin dose by 10-20% 2
• If a patient has hypoglycemia unawareness or experiences severe hypoglycemia (requiring assistance), glycemic targets should be raised to strictly avoid further hypoglycemia 1

Monitoring Recommendations

• Regular blood glucose monitoring before meals is essential for patients on insulin therapy 1
• Continuous glucose monitoring (CGM) may be used to assess glycemic targets and identify patterns of hypoglycemia 1
• For patients not meeting A1C goals despite reaching preprandial glucose targets, postprandial glucose monitoring (1-2 hours after meals, target <180 mg/dL) may be helpful 1

Common Pitfalls to Avoid

• Maintaining the same insulin dose despite low premeal glucose readings significantly increases hypoglycemia risk 2
• Overbasalization (basal insulin dose >0.5 units/kg/day) can lead to frequent hypoglycemia and high glucose variability 1, 2
• Using sliding scale insulin alone is inadequate for most patients with T2DM and should be combined with basal insulin for optimal control 1
• Premixed insulin therapy has been associated with higher rates of hypoglycemia and should be used cautiously 1, 2

Remember that while achieving glycemic targets is important, avoiding hypoglycemia is equally critical for patient safety and long-term outcomes. Regular monitoring and appropriate insulin dose adjustments are essential components of effective diabetes management.